JAVA FINAL 16
What must every line of code not followed by curly braces end in?
";"
grouping operator
( ), highest precedence
{ }
(Curly braces). Marks the beginning and end of a unit, including a class or method description.
Named constant:
A memory location whose content is not allowed to change during program execution.
Binary operator:
An operator that has two operands.
&&
And(both are true)
Layering Reader Classes
BufferedReader in = new BufferedReader( new FileReader(path))
ALL UPPERCASE IN JAVA
CONSTANTS
Inheritance
How one class can be created from another.
A variable declared in a method is said to be a ____________________.
Local variable
return type of constructor
NONE...not even void
Assignment operator:
The = (the equals sign). Assigns a value to an identifier.
println
a method that prints characters to the screen and moves to the next line
Virus
a program that can enter a computer and perhaps destroy information
public class _____
class header; indicates a publicly accessible class named "_____"
get a file
import java.io.* public static void getAFile(String filename) { try{ FileInputStream file = new FileInputStream(filename);} }
access modifier
says where a class can be used or referenced
public interface Pet
syntax to create an interface called Pet
String combination identifier
"+"
How do you assign data to a variable?
"=". ex. int number = 100
When defining a method, the _____ parameter is a name used for the calling object.
"this."
remainder or modulus operator
%, fourth highest precedence, left to right association
way to genericize new Fragment();
(TO) createFragment() take constructor form and replace with function to genericize (refactor)...but either have to define function right there, or create abstract stub, making class abstract
cast operator
(double),(int), third highest precedence, right to left association
s is a string. Expression whose value is true if & only if the value comes bw "mortgage" & "mortuary" in the dictionary.
(s.compareTo("mortgage") > 0 && s.compareTo("mortuary") < 0 )
Cast
(typeName) expression
assign userInput to a variable
(within if statement) int numberEntered = userInput.nextInt(); ...also Line, Boolean, Float
What operator multiplies two numbers?
*
multiplication operator
*, fourth highest precedence, left to right association
addition operator
+, fifth highest precedence, left to right association
unary plus operator
+, third highest precedence
pre-test loops
- for construct - while construct
subtraction operator
-, fifth highest precedence, left to right association
unary minus operator
-, third highest precedence
Mixed Mode Conversion
-Convert to LARGEST DATA TYPE -does not allow from more accurate to less accurate
post-test loop
-do while construct
switch construct
-expr must eval to char, byte, short or int types -case values must be literals/constants + unique -include BREAK after case
method selector operator
., second highest precedence, left to right association
How to use sub-string function?
...
equals upper or lower case
.equalsIgnoreCase()
other scanner (static) object methods
.hasNextBoolean() .hasNextFloat() .hasNextDouble()
What operator divides two numbers?
/
division operator
/, fourth highest precedence, left to right association
What symbols are used to make comments in Java? (Both single and block comments)
// and /* */
boolean
1 bit primitive that manipulates the two logic value T and F.
byte
1 byte, stores an integer
What are checked & unchecked exceptions.
1) Checked Exception is required to be handled by compile time while Unchecked Exception doesn't. 2) Checked Exception is direct sub-Class of Exception while Unchecked Exception are of RuntimeException.
interfaces vs abstract class
1) abstract class and interface cannot be instantiated...a class implements an interface, or an interface extends an interface, but an interface cannot implement an interface. 2) an interface specifies a "contract", and all method stubs must be implemented (or at least overridden in subclass) 3) public and abstract are automatically added to every interface method, and abstract is implicitly (& automatically) added to entire interface. 4) in interface, NO method is allowed to have a body
2 main benefits of abstraction
1) good design, 2) (unintended) security in that hackers are not going to guess setCartesianCoordinates(integer x, integer y); but would rather first guess setX(integer x);
Name 3 reasons why favor composition over inheritance
1. Almost all inheritance can be rewritten 2. Less about modeling the real world and more about modeling interactions in a system and roles and responsibilities 3. Inheritance is difficult to maintain V52
Describe 2 classes can have.
1. Is a - inheritance 2. Has a - composition / aggregation V47
Create an array called 'colors' and add to it :"red","blue", "Green" 2. 1. Create a foreach loop the writes out the contents of the arra
1. String[] colors = new String[] {"red","blue", "Green"}; 2. for (String c : colors){ System.out.println(c); } v42
Name to things about strings in Java.
1. Treated like a primitive type (can be assigned w/o the New keyword) but it's an object 2. They're immutable (can't be changed). If you give a string a different value, it create an new string in memory. Java Fundamentals - v22
Reasons to use "double"
1023 digits after the decimal point
Reasons to use "float"
127 digits after the decimal point
short
2 bytes, stores integer values
int
4 bytes, stores integer values
float
4 bytes, stores less precise floating-point numbers
long
4 bytes, stores long integer values
What is the ASCII value of 'A'?
65
byte (signed) short (signed) int (signed) long (signed) float double char boolean
8 bits > -2^7 to 2^7 -1 16 bits > -2^15 to 2^15 -1 32 bits > -2^31 to 2^31 -1 64 bits > -2^63 to 2^63 -1
Byte
8 bits. smallest unit of storage in memory
double
8 bytes, stores floating-point numbers
What is the ASCII value of 'a'?
97
In Java, every program statement ends with what?
; (a semicolon)
What are 6 assignment operators?
= += -= *= /= %= ----------------- v20
Logical ops: !expr __ & __ __&&__ __^__ __ | __ __||__
= NOT (evaluates from RIGHT to LEFT) = logical AND' = conditional AND = logical exclusive OR (either not both) = logical inclusive OR = conditional OR
assignment operator
=, lowest precedence, right to left association
Instantiate
=new
Identifier:
A Java identifier consists of letters, digits, the underscore character ( _), and the dollar sign ($), and must begin with a letter, underscore, or the dollar sign.
key
A ____ is an identifier used to reference, or look up, a value in a data structure.
JDK
A bundled set of development utilities for compiling, debugging, and interpreting Java Applications.
What must a class name always start with?
A capital letter then camel case with no spaces.
Escape Sequences
A character preceded by a backslash is an escape sequence ~ \t = tab ~ \b = backspace ~ \n = new line ~ \r = carriage return
BufferedReader
A class. Read text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines.
Expression
A construct made up of variables, operators, and method invocations, which are constructed according to the syntax of the language, that evaluates to a single value.
Screen coordinate system
A coordinate system used by most programming languages in which the origin is in the upper-left corner of the screen, window, or panel, and the y values increase toward the bottom of the drawing area
boolean
A data type that represents a true or false value.
double
A data type that represents decimals.
int
A data type that represents whole numbers.
DataSource
A factory for connections to the physical data source that this DataSource object represents.
Source file:
A file containing the source code, having the file extension .java.
Method
A group of programming statements given a name.
block
A group of zero or more statements between balanced braces and can be used anywhere a single statement is allowed.
What is a 'set' in Java?
A grouping like a LIST but all the items are unique. There are no duplicates.
What's a list in Java?
A grouping that is ordered, sequential & can have duplicates.
Variable
A location in memory used to hold a data value.
Variable:
A memory location whose content may change during program execution.
b()
A method called b
accessor method
A method that gets the value of an instance variable without altering the state of the variable/object.
Relative Path
A path that is not anchored to the root of a drive. Its resolution depends upon the current path. Example ../usr/bin.
Programming:
A process of planning and creating a program.
ResultSet
A public interface. A table of data representing a database result set, which is usually generated by executing a statement that queries the database.
An object is this type of variable
A reference variable
Computer program:
A sequence of statements whose objective is to accomplish a task.
Escape Sequence
A sequence used to represent special characters.
Programming language:
A set of rules, symbols, and special words.
Data type:
A set of values together with a set of operations.
Transistors
A solid state device that has no mechanical or moving parts; the light switch of electricity flow
Constructor?
A special type of method that is called when an object is created to initialize variables.
Assignment Statement
A statement assigning a value to a variable.
Register
A storage cell that holds the outcome of an arithmetic operation
Pseudocode
A stylized half-English, half-code language written in English but suggestion Java code
switch case vs if else
A switch compiles into a lookup table which is fundamentally different then the if/else statements. If the last statement in a if/else chain is the one you want you have to check all the previous if/else first. This is not the case with a switch
Attribute
A value an object stores internally.
Literal
A value represented as an integer, floating point, or character value that can be stored in a variable.
Object Reference
A value that denotes the location of an objection in memory. A variable whose type is a class contains a reference to an object of that class
Sentinel
A value that tells us to stop looping
The BitSet class also provides other methods for performing comparisons and bitwise operations on sets such as:
AND, OR, and XOR
name [row] [col]
Access an element
. operator
Access fields
1. A(n) -______- allows the application class to retrieve the value of an instance variable.
Accessor Method Call
Private instance variables can be accessed from outside their class through ______ methods and changed with _________ methods
Accessor methods && Mutator methods
J2EE
Acronym for Java 2 Platform, Enterprise Edition.
J2ME
Acronym for Java 2 Platform, Micro Edition.
J2SE
Acronym for Java 2 Platform, Standard Edition.
6. A(n) -______- is the value sent to a method.
Actual Parameter
Concatenation
Adding one string to another.
Scanner input = new Scanner(System.in);
Adds scanner to program
.java
All Java file names have to have this extension.
Capital Letter
All java file names must have this at the beginning.
Defining a variable
Allocates memory for storage
What are bounded types in Java?
Allows you to restrict the types that can be used in generics based on a class or interface. v60
StringBuffer
Alters immutability
Passing by reference
An Array is - it passes info about where the array is stored in memory
StackTraceElement
An element in a stack trace, as returned by Throwable.getStackTrace(). Each element represents a single stack frame. All stack frames except for the one at the top of the stack represent a method invocation. The frame at the top of the stack represents the the execution point at which the stack trace was generated. Typically, this is the point at which the throwable corresponding to the stack trace was created.
classpath
An enviroment variable that includes an argument set telling the Java virtual machine where to look for user defined classes/packages.
JRE
An environment used to run Java Applications. Contains basic client and server JVM, core classes and supporting files.
Run-time error
An error that occurs when a program asks the computer to do something that it considers illegal, such as dividing by 0
Mixed expression:
An expression that has operands of different data types.
Object
An instance of a class.
Unary operator:
An operator that has only one operand.
String Literal
Anything within double quotation marks.
18. A call to the toString method would appear in the -______-.
Application class
Methods?
Are always public. They return data. Methods are made so that you can call on them so that you can use its functionality.
Parameters are filled in with _________________ when invoking a method.
Arguments
exception types
ArithmeticException ClassNotFoundException IllegalArgumentException IndexOutOfBoundsException(s) InputMismatchException
ArrayList eg
ArrayList<String> names = new ArrayList(); names.add = "John Smith"; names.add = "Pete Wendell"; names.add = "Alicia James"; these are added just as they would be in an array, with John smith at index 0, pete at index 1... however, i can also do names.add(2, "Harvey Dent"); which must current 2 index to right...
20. A(n) -______- stores a value in a variable.
Assignment Statement
Declaring a variable
Associates variable's name with type ~DOES NOT ALLOCATE MEMORY FOR STORAGE
Name 9 primitive types
BSILF DB CS byte short int long float double boolean char String
Naming Methods?
Begins with public then is whatever data is going to be returned. ex. public String displayname()
Scope
Block of code in which a variable is in existence and may be used.
&&
Boolean operator meaning both sides have to be true. A Short circuiting logical operator.
||
Boolean operator meaning only one side has to be true. A Short circuiting logical operator.
int
By default, the int data type is a 32-bit signed two's complement integer, which has a minimum value of -231 and a maximum value of 231-1. In Java SE 8 and later, you can use the int data type to represent an unsigned 32-bit integer, which has a minimum value of 0 and a maximum value of 232-1. Use the Integer class to use int data type as an unsigned integer. See the section The Number Classes for more information. Static methods like compareUnsigned, divideUnsigned etc have been added to the Integer class to support the arithmetic operations for unsigned integers.
What does the 'new' key word do here when creating an instance? Printer myPrinter = new Printer();
Calls the default constructor on the Printer class.
String
Can use +, ., and +=
Conversion
Changing one type of primitive data to another.
What are the TWO types of data contained by classes?
Characteristics and Behavior
16. The -______- contains the method header and the method body.
Class Method
RuntimeException
Class is the superclass of those exceptions that can be thrown during normal runtime of the Java virtual machine.
InterruptedException
Class. Thrown when a thread is waiting, sleeping, or otherwise paused for a long time and another thread interrupts it using the interrupt method in class Thread.
Object Construction
ClassName objectName = new ClassName(parameters);
Static method call
ClassName.methodName(parameters);
In OOP, describe is-a or has-relationships?
Classes in OOP, are related to each other & they're going to be related through an "IS-A" relationship or "HAS-A" relationship. > IS-A relationship result from inheritance > HAS-A relationship result from composition This comes from the need to reuse code. v47
ArrayList<Type>()
Constructor: Creates an empty ArrayList with an initial capacity of 10
ArrayList<Type>(int n)
Constructor: Initial capacity to hold n objects
Character types (char)
Contain single character value stored as unicode characters
new type [nRows] [nCols]
Create a 2D array
Instantiating
Creating an object
Instantiation
Creating an object.
Overloading the method?
Creating multiple definitions for the same method name, using different parameter types
14. The -______- specifies what information can be stored in a variable and what operations can be performed on it.
Data Type
Encapsulation?
Data and actions combined into a class whose implementation details are hidden
17. Instance variables are found in the -______-.
Declaration Statement
type[] [] name
Declare a 2D array
2. A(n) -______- is called when an object is instantiated and there are no arguments to be sent.
Default Constructor
Object-oriented programming
Designing a program by discovering objects, their properties, and their relationships
Operator precedence rules:
Determine the order in which operations are performed to evaluate an expression.
Static classes
Dont have instances
Surround all String text with?
Double Quotes
element
Each item in an array
What is camel casing?
Each time a new word begins start it with a capital letter
Primitive Data Types
Eight commonly used data types.
Double var = input.nextDouble();
Establishes value inputed into scanner as a variable
matrix.length pixels.length
Example of getting the number of rows
matrix[3] [2] = 8; pixels[r] [c] = aPixel;
Example of setting the value of elements
int value = matrix [3] [2]; Pixel pixel = pixels[r] [c];
Example: Accessing two elements
matrix[0].length pixels[0].length
Example: get the number of columns
int [] [] matrix Pixel [] [] pixels
Examples of 2D array declarations
new int [5] [8] new Pixel [numRows] [numCols]
Examples of creation of 2D arrays
a.b()
Execute a method b which belongs to object a
Exercise: 1. Create a printer class w/ a modelNumber property & a method to print that model #. 2. From you main method, assign a value to the modelNumber & invoke the Print() method.
Exercise. v(32)
Creating a File object
File f = new File(pathName);
Output Stream
Flows data from a program out to some external device
Input Stream
Flows data from some external device into a program
11. In a method header, the -______- specifies the type of data the method will send back to the caller.
Formal Parameter
name[0].length
Get the number of columns
name.length
Get the number of rows
joke about hacking into a bank without abstraction
Go to my account's global context and type setBalance()
What must variable names have/not have?
Have: Starts with a lower case letter. Not Have: after initial letter cannot have a symbol other than the underscore (no spaces).
Constants
Identifiers that always have the same value.
import java.util.Scanner;
Import the ability to use a scanner from database
Using Underscore Characters in Numeric Literals
In Java SE 7 and later, any number of underscore characters (_) can appear anywhere between digits in a numerical literal.
What is a primitive type in Java?
In java, we have primitive types & objects. Primitive types hold the actual value in memory. Object hold references in memory.
Static keyword
Indicates a class variable vs. an instance variable
3. A(n) -______- stores the data for an object.
Instance Variable
Objects have both _______ and _______.
Instance Variables && Methods
convert integer or any other type toString
Integer.toString(bigInt); Integer.parseInt(intString); -- this converts it back???
memory address register
It is 32 bits. Used in memory write and read operations and not accessible by the programmer.
What's the purpose of the Finally Block
It's useful to force code to execute whether or not an exception is thrown. It's useful for IO operations to close files.
;
Like a period in English. Marks the end of a statement or command
public static void main(String[] args){
Line 2 of program, opens programming block
LinkedList vs ArrayList
LinkedList compares favorably to ArrayList when adding and deleting objects from list a lot However, LinkedList is not as efficient at accessing ArrayList objects by index...when listening to video...he uses exact same methods on LinkedList as he did on ArrayList, so will have to check documentation (banas 12)
8. A variable that is declared inside a method and can only be used within that method is called a(n) -______- .
Local Variable
Define how java classes are connected.
Loosely connected objects that interact with each other.
Encapsulation
Making some data and methods inaccessible to outsiders ~public: visible anywhere ~private: visible only to other class members ~protected: visible to class and subclass w/i pkg
What's the equivalent of a dictionary in Java? Please create an example.
Map - Look in module about collections.
immutable
Means that once created, their values cannot be changed.
void
Means that the method does something but does not return any value at the end
9. A(n) -______- tells the computer to execute a method.
Method Call
19. A(n) -______- appears inside the parentheses of a method header, and contains a data type and a name.
Method Definition
hasMoreElements
Method of Enumeration. Tests if this enumeration contains more elements.
put
Method of Hashtable. Maps the specified key to the specified value in this hashtable.
remove
Method of Hashtable. Removes the key (and its corresponding value) from this hashtable.
containsKey
Method of Interface Map. Returns true if this map contains a mapping for the specified key.
start
Method of Thread. This method Causes this thread to begin execution; the Java Virtual Machine calls the run method of this thread.
enumerate
Method of ThreadGroup. Copies into the specified array every active thread in this thread group.
run
Method. When an object implementing interface Runnable is used to create a thread, starting the thread causes the object's this method to be called in that separately executing thread.
All objects in a class have the same _______ and same types of _______.
Methods && Instance Variables
13. A(n) -______- allows the application class to change the value stored in an instance variable.
Mutator Method
A no-argument constructor has....
No parameters.
if you call the next() method from the iterator interface and there are no more elements next() throws what exception?
NoSuchElementException
Reasons to use "int"
Numbers -2 billion to, 2 billion
Reasons to use "long"
Numbers greater then ±2 billion
4 Java Data Types?
Numeric, String, Character, Boolean.
*** If a variable is used as an argument...
ONLY the value of the the argument is plugged into the parameter, NOT the variable itself
10. An instance method must be called on a(n) -______- .
Object
Define the Java related "object" and what is it interchangeable with?
Object and class define state (data_ and behavior (operations). Classes define an object's behavior.
A class is a type whose values are ______
Objects
Private variable declaration?
Only applies to that class. ex. private String first;
public class{
Opens and names your program
Overriding vs Overloading
Overriding when return type, name, parameters the same. Overloading when name the same but parameters different. (overloading is illegal when extending a superclass)
A _____________ is like a blank in a method definition...
Parameter
What is assumed to be true when a method is called
Precondition
Method
Prewritten code to accomplish a task
7. The memory location that stores a value sent to a method is called a(n) -______-.
Primitive Variable
Layering Writer Classes
PrintWriter out = new PrintWriter( new BufferedWriter( new FileWriter(path)));
System.out.print(" ");
Prints a string of text
If an instance variable or method is _____ then it cannot be directly referenced anyplace except in the definition of a method of the same class.
Private
Default Class Constructor
Provided by java w/o arguments and invoked when there is no constructor
15. A(n) -______- stores the address of an object.
Reference Variable
12. A(n) -______- sends a value back to the caller.
Return Statement
return function?
Returns and expression. ex. return first + " " + middle + " " + last;
Syntax
Rules for combining words into sentences
Semantics
Rules for interpreting the meaning of statements
How to declare variables with the same data type on the same line?
Separate them with commas. ex. int number, salary, hoursWorked; (end with semi-colon)
Stream
Sequence of bytes that flow into or out of a program
Bit pattern
Series of 0's and 1's
Java vocabulary
Set of all words and symbols in the language
Method
Set of code that performs well-defined function
name [row] [col] = value
Set the value of an element
long totalMilliseconds = System.currentTimeMillis();
Sets total number of milliseconds since midnight, January 1, 1970, as a variable
Constructor
Special kind of method, build up an instance of a class
Object
Special kind of variable containing DATA and METHODS
Class Constructors
Special methods commonly used to initialize objects when they are created
things to do when refactoring (a class with redundancies)
SpecificClass whatever = new SpecificClass(); becomes a function SpecificClass whatever = createSpecificClass();
statement
Statements are roughly equivalent to sentences in natural languages. A statement forms a complete unit of execution.
What non-numeric data type can have class operations preformed to it?
String
What word is always capitalized in java syntax?
String
0 or more characters surrounded by double quotes?
String (always capital "S")
Example of variable declaration and explanation.
String firstName; Start with data type then variable name. Must end with the ";".
Example of how to retrieve the last string added to the vector:
String s = (String)v.lastElement();
Example of how to "get" a vector element using an index:
String s1 = (String)v.get(0); ( you must cast the returned element bc by default vectors are designed to work with the Object class
How could you define a String variable named wrd and initialize it to the word cats?
String wrd = "cats";
Multidimensional arrays
String[][] names = { {"Mr. ", "Mrs. ", "Ms. "}, {"Smith", "Jones"} };
Set of print commands to print to the console on two different lines?
System.out.print("Hello"); //no "ln" System.out.print("World"); //Has the "ln"
print the ARRAY moreNames
System.out.print(Arrays.toString(moreNames)); toString must be a static method...
Print to screen
System.out.println("Hello World!");
Command to print to the console? (what letter is capitalized)
System.out.println("Hello");
What System.out method moves the cursor to the next line?
System.out.println()
Given: String firstName = "reynald"; Writhe the line of code to out the index of letter 'a'
System.out.println(firstName.indexOf('e')); v23
Create a generic class as in v58
TODO
Create a generic method as in v59 and use bounded types (v60)
TODO
Create an example of Polymorphism that reflect v51
TODO
Create an example of changing inheritance to composition by using interfaces. See exampled in v54.
TODO
Create an example of composition. Create a car class that HAS a gas tank. After the car runs 200miles, make it request to add gas.
TODO inspired by v49 (paper tray example)
Create an example of inheritance and using a constructor by writing a method that print the name passed into the constructor. In the super class, use the keyword 'protected'
TODO v48
Create an example using 'wild cards'
TODO v61
What is erasure?
TODO v62
Create an IllegalAurgumentException (with some error message) in a method & on the calling method, add a try / catch block to display your error.
TODO - video on Excepions -->Try / Catch
What is a 'Queue' in Java?
TODO: Create a queue
What does empty Parenthesis at the end of a method declaration mean?
That the data for the method will be put in later.
Copying Arrays
The System class has an arraycopy method that you can use to efficiently copy data from one array into another: public static void arraycopy(Object src, int srcPos, Object dest, int destPos, int length) The two Object arguments specify the array to copy from and the array to copy to. The three int arguments specify the starting position in the source array, the starting position in the destination array, and the number of array elements to copy.
boolean
The boolean data type has only two possible values: true and false. Use this data type for simple flags that track true/false conditions. This data type represents one bit of information, but its "size" isn't something that's precisely defined.
byte
The byte data type is an 8-bit signed two's complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive). The byte data type can be useful for saving memory in large arrays, where the memory savings actually matters. They can also be used in place of int where their limits help to clarify your code; the fact that a variable's range is limited can serve as a form of documentation.
char
The char data type is a single 16-bit Unicode character. It has a minimum value of '\u0000' (or 0) and a maximum value of '\uffff' (or 65,535 inclusive).
Source code:
The combination of the import statements and the program statements
Class
The data type of an object
double
The double data type is a double-precision 64-bit IEEE 754 floating point. Its range of values is beyond the scope of this discussion, but is specified in the Floating-Point Types, Formats, and Values section of the Java Language Specification. For decimal values, this data type is generally the default choice. As mentioned above, this data type should never be used for precise values, such as currency.
float
The float data type is a single-precision 32-bit IEEE 754 floating point. Its range of values is beyond the scope of this discussion, but is specified in the Floating-Point Types, Formats, and Values section of the Java Language Specification. As with the recommendations for byte and short, use a float (instead of double) if you need to save memory in large arrays of floating point numbers. This data type should never be used for precise values, such as currency. For that, you will need to use the java.math.BigDecimal class instead. Numbers and Strings covers BigDecimal and other useful classes provided by the Java platform.
Polymorphism
The idea that we can refer to objects of different but related types in the same way.
long
The long data type is a 64-bit two's complement integer. The signed long has a minimum value of -263 and a maximum value of 263-1. In Java SE 8 and later, you can use the long data type to represent an unsigned 64-bit long, which has a minimum value of 0 and a maximum value of 264-1. Use this data type when you need a range of values wider than those provided by int. The Long class also contains methods like compareUnsigned, divideUnsigned etc to support arithmetic operations for unsigned long.
Operator Precedence
The rules that govern the order in which operations are done.
short
The short data type is a 16-bit signed two's complement integer. It has a minimum value of -32,768 and a maximum value of 32,767 (inclusive). As with byte, the same guidelines apply: you can use a short to save memory in large arrays, in situations where the memory savings actually matters.
Token:
The smallest individual unit of a program written in any programming language.
Boolean Literal
The words true and false.
Threads
These share the process's resources, including memory and open files. This makes for efficient, but potentially problematic, communication.
Error
This Class indicates issues that an application should not try to catch. Subclass of the class Throwable.
Vector
This class implements a growable array of objects. Like an array, it contains components that can be accessed using an integer index. However, the size of a this can grow or shrink as needed to accommodate adding and removing items after the this has been created.
Exception
This class indicates issues that an application may want to catch. A subclass of the class Throwable.
Object
This class is the root of the class hierarchy. Every class has this as a superclass. All objects, including arrays, implement the methods of this class.
Hashtable
This class maps keys to values. Any non-null object can be used as a key or as a value. To successfully store and retrieve objects, the objects used as keys must implement the hashCode method and the equals method.
ThreadGroup
This class represents a set of threads.
Context
This interface consists of a set of name-to-object bindings. It contains methods for examining and updating these bindings.
Enumeration
This interface generates a series of elements, one at a time. Successive calls to the nextElement method return successive elements of the series.
Runnable
This interface should be implemented by any class whose instances are intended to be executed by a thread. The class must define a method of no arguments called run.
writeObject
This method is used to write an object to the stream. Any object, including Strings and arrays, is written with this method. Multiple objects or primitives can be written to the stream. The objects must be read back from the corresponding ObjectInputstream with the same types and in the same order as they were written.
notifyAll
This method wakes up ALL waiting threads; the scheduler decides which one will run
notify
This method wakes up a single thread which is waiting on the object's lock
javax.swing.*;
To create lightwieght components for a GUI.
java.net.*;
To develop a networking application.
java.awt.*;
To paint basic graphics and images.
java.io.*;
To utilize data streams.
java.lang.*;
To utilize the core java classes and interfaces.
java.util.*;
To work with collections framework, event model, and date/time facilities.
T or F: The name of a local variable can be reused outside of the method in which it is declared ?
True
True or false, BitSets automatically grow ti represent the number of bits required by a program?
True?
Buffered Streams
Use a large block of memory to store batches of data that flow into or out of a program
When using primitive types with ArrayList
Use class Integer
Cast operator:
Used for explicit type conversion
Boolean type (boolean)
Used in conditional tests to control execution flow- TRUE or FALSE
//
Used to comment out a line.
/* */
Used to comment out a paragraph or longer
double
Used to declare and initialize a fraction interager. Ex: double canVolume = 0.335;
int
Used to declare and initialize a non fraction interager Ex: int canVolume = 5;
byte
Used to define a primitive variable as an integer with 1 byte of storage. Also a corresponding wrapper class.
==
Used to equal a value
Method Overloading
Using methods with the same name but different # and types of arguments
Object
Value of a class type. Stores its state in fields and exposes its behavior through methods
Constant
Variable whose value cannot be changed once initialized (final)
Class Variables
Variables associated with ENTIRE class
Instance Variables
Variables associated with each object from a class - stored in separate mem location
similar to a traditional Java array, except that it can grow as necessary to accommodate new elements and also shrink.
Vector
Example of a vector that has an initial size of 25 and expands in increments of 5 elements when more than 25 elements are added to it:
Vector v = new Vector(25, 5);
A class in the Java API
What is an ArrayList?
Java libraries
What is the Java API?
Post Condition?
What will be true after a method is called
Void
When a method does not return a value.
Implicit type coercion:
When a value of one data type is automatically changed to another data type.
Encapsulation
When each object protects its own information.
Reserved words
Words that have predefined meanings that cannot be changed
What escape sequence makes one backslash character in a print or println statement?
\\
What escape sequence makes the backspace character?
\b
What escape sequence makes the newline character?
\n
What escape sequence makes the tab character?
\t
bit
a binary digit that is the smallest unit of information. 1 or 0.
truth table
a breakdown of logic functions by listing all possible values
true
a class that has even one abstract method must be marked as an abstract class
System
a class that holds objects/methods to perform system-level operations, like output
What does /* suggest
a comment
Hash code
a computed key that uniquely identifies each element in a hash table.
array
a container object that holds a fixed number of values of a single type. The length of an array is established when the array is created.
load factor
a floating-point number between 0.0 and 1.0 that determines how and when the hash table allocates space for more elements.~258PDF
Coordinate system
a grid that allows a programmer to specify positions of points in a plane or of pixels on a computer screen
method
a group of one or more programming statemetnts that collectively has a name
Package
a group of related classes in a named directory
A local variable disappears when...
a method invocation ends.
a method that prints characters to the screen and remains on the same line
class
a programmer defined data type. Blueprint from which individual objects are created. A class definition defines instance and class variable and methods. also specifies interfaces
Arithmetic expressions
a sequence of operands and operators that computes a value
Class
a set of instructions that create an object
Debugging
a step by step method of testing a program and correcting programming errors
control unit
a subsystem of the processor that can 1. fetch next instructions 2. decode them 3. execute them
algorithm
a well ordered collection of unambiguous and effectively computable operations that when executed produces a result and halts in a finite amount of time
method types allowed in abstract class
abstract (no body), or non-abstract...whereas interface defines ONLY abstract methods
Constructor Definition
accessSpecifier ClassName(parameterType paramterName, ...) { constuctor body }
Instance Field Declaration
accessSpecifier class ClassName { accessSpecifer fieldType fieldName; }
Class Definition
accessSpecifier class ClassName { constructors methods fields }
Method Definition
accessSpecifier returnType methodName(parameterType parameterName, . . .) { method body }
way to get private variables from another class
accessor methods
add() remove()
add something to ArrayList remove something to ArrayList
Write an expression that returns the position of the 1st occurrence of the String "Avenue" in address (a String).
address.indexOf("Avenue")
Type casting
allows one data type to be explicitly converted to another
Iteration construct/Loops
allows program to repeatedly execute instructions
concatenation operator
allows strings to be combined in Java
do(loop)
always execute once and keep executing while condition is true
ASCII
american standard code for information interchange. an international standard for representing textual info. 8 bits/character. allows a total of 256 character to be represented
Exception
an abnormal state or error that occurs during runtime and is signaled by the operating system
argument
an actual parameter in a method call or one of the values combined by an operator
Logic error
an error such that a program runs, but unexpected results are produced. Also referred to as a design error
What is an object in Java
an instance of a class
'this' refers to
an instance of the class. thus, 'this' cannot refer to static methods, which
parameter
an item of info specific to a method when the method is called
instance
an object of a particular class. Created using the new operator followed by the class name
out
an object that provides a way to send output to the screen
Create an array
anArray = new int[10];
Get the length of an array
anArray.length
Initialize an array
anArray[0] = 100; or int[] anArray = { 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 };
numeric data types
another name for primitive data types; most commonly int and double
Boolean expression
any expression that evaluates to true or false
instance variable
any item of data that's associated with a particular object.
white space
any sequence of only space, tab, and newline characters
String concatenation
append a string or value to another string
ALU
arithmetic/logic unit. sub system that performs math and logical operations.
Array Element Access
arrayReference[index]
Arithemetic overflow
assigning a value to a variable that is outside of the ranges of values that the data type can represent
initialize
assigning a value to a variable when it's created
b
b
\\
backslash; causes a backslash to be printed
binary
base 2 positional numbering system composed of 1s and 0s
b
bb
Block
between two curly braces
Binary Seach
binarySearch(array, lowerboundIndex, upperboundIndex, key) public static void binarySearch(int[ ] array, int lowerbound, int upperbound, int key) { int position; position = ( lowerbound + upperbound) / 2; while((array[position] != key) && (lowerbound <= upperbound)) { comparisonCount++; if (array[position] > key) // If the number is > key, .. { // decrease position by one. upperbound = position - 1; } else { lowerbound = position + 1; // Else, increase position by one. } position = (lowerbound + upperbound) / 2;
constructor
block statement created when an object is declared
True False data type
boolean
Bubble Sort
boolean flag = true; int n []; for (int i = 0; i < n.length; i++) { if(!flag) break; flag = false; for(int j = 0; j < n.length - i; j++) { if(numLis[n] > numList[i+1] { int temp = numList[i]; numList[i] = numList[i++]; flag = true; } }
Example of how to use the contains method when working with hashtables:
boolean isThere = hash.contains(new Rectangle(0, 0, 5, 5));
Example of how to get the value of a individual bit in a set:
boolean isWriteable = connex.get(ChannelAttributes.WRITABLE);
Object oriented programming
building programs by creating, controlling, and modifying one or more objects
print vs println
carriage return
The next() method always returns an object of the class Object.To get around this you can _____ the object into a more appropriate object.~223
cast
how to set up try catch for exceptions
catch most specific first catch (FileNotFoundException e) {System.out.println("file not found"} catch (IOException e) {...} catch (Exception e) {...}
/b
causes the cursor to back up, or move left, one position
Alphabetic characters that can be stored as a numeric value?
char
Braces
characters used to mark the beginning and end of blocks of code
final keyword
code cannot be changed(overridden) by subclass
ArrayList<string> stringList = new ArrayList<string>();
code to declare a string array list called stringList
public class Triangle extends Shape
code to make triangle subclass from Shape superclass
Method returning an integer greater than, equal to, or less than 0 to indicate whether this string is greater than, equal to, or less than s1.
compareTo(s1) - it compares character by char. until difference in string letters found. - Then → returns an integer representing the difference in characters
Software
computer instructions or data. Anything that can be stored electronically
arithmetic expression
consists of operands and operators combined in a manner familiar from algebra
instantiation
construction of an object of that class
method, which simply checks whether an element is in the vector:
contains() (example:boolean isThere = v.contains("Webb");] )
continue vs break in a while loop
continue jumps back up to while, break jumps down out of while loop.
cast
converting a value from one type to another explicitly
Procedural programming
creating a program by using a step by step process to perform specific tasks
Variable declaration statement
declares the identifier and data type for a variable
semantics
define the rules for interpreting the meaning of statements
Semantic rules:
determine the meaning of instructions in a programming language.
Syntax rules:
determine the validity of instructions in a programming language.
For numeric data types what declaration will always be used?
double
How could you define a real number named numero and initialize it to 867.5?
double numero = 867.5
Insert a comment? On multiple lines?
double slash ex. //commented slash asterisk ex. /* one line two lines */ (its the back slash for both)
//
double slash; marks the beginning of a comment (a statement ignored by the computer)
how to give location of error
e.printStackTrace();
Random Access Memory
electronic circuits in a computer that can store code and data of running programs
==
equal to
Your classes should generally have both an _______ method and a _____ method.
equals && toString
Method returning true if this string is = to string 2
equals(s1)
\\
escape character for backslash
static variables
essentially global variables...when a member is declared static it can be accessed before any instance of its class is created and without reference to any object....static variables can be shared by multiple classes, but changing the static variable in one place changes it globally.
class Object
every class in Java is either a direct or indirect subclass of what?
import java.util import javax.swing
example java api package imports
Comments
explanatory sentences inserted in a program in such a manner that the compiler ignores them
actual parameters
expression supplied by a formal parameter of a method by the caller. Value of the parameter.
Mixed-mode arithmetic
expressions imvolving integers and floating-point values
implement an abstract class
extends public class Vehicle extends Crashable implements Drivable {}
CallableStatement
extends PreparedStatement. The interface used to execute SQL stored procedures. The JDBC API provides a stored procedure SQL escape syntax that allows stored procedures to be called in a standard way for all RDBMSs. This escape syntax has one form that includes a result parameter and one that does not. If used, the result parameter must be registered as an OUT parameter. The other parameters can be used for input, output or both. Parameters are referred to sequentially, by number, with the first parameter being 1.
Members
fields(data the class holds), methods
Constant definition
final typeName variableName = expression;
indexOf() size()
find out where something is in ArrayList get number of elements in ArrayList
primitive data types
first category of Java variables such as numbers, characters, and Booleans
a Boolean value that represents one of a group of on/off type states in a program.
flag
FLOPS
floating point operations per second. measure of computer's performance at brute force applications
Example of how to loop through a entire vector using the iterator class :
for (Iterator i = v.iterator(); i.hasNext(); ) { String name = (String) i.next(); System.out.println(name); }
The "for each" loop
for (Type variable: collection) statement;
The for Statement
for (initialization; condition; update) statement;
"for loop" syntax
for (iterator initialization; iterator comparison; iterator incrementalization) {}
adjective name
for interfaces (modify a class, which is usually a noun) eg, public interface Drivable{}
Pass by value
for primitive data types
memory
function unit of a computer that stores and retrieves instructions and data
Accessors
get() methods
Naming standard for accessor method?
getABC();
Arguments
give method more info about what to do
Applets
graphics in java
what is overloading a method
having two methods with same name...the key is the methods must have different parameters
encapsulation
hiding of implementation details
Memory Data Register
holds the information to be transferred/copy of information received
/t
horizontal tab; causes the curson to skip over to the next tab stop
packages
how are classes grouped in java?
super.method();
how to call a superclass method in a subclass
how to do: if (x != false) {}
if (!(false)) this will run fortunately. however if (l
The if Statement
if (condition) statement; else statement;
String variables name1 & name2 Write a fragment of code assigning the larger of the 2 to the variable first (NOTE: "larger" here means alphabetically larger, not "longer". Thus, "mouse" is larger than "elephant" bc "Mouse" comes later in the dictionary than "elephant"!)
if (name1.compareTo(name2) > 0 ) { first = name1; } else { first = name2; }
Hashable class
implements Dictionary, an abstract class that defines a data structure for mapping keys to values. This is useful when you want to access data through a particular key rather than an integer index.
Stack class
implements a last-in, first-out stack of elements. You can think of a stack literally as a vertical stack of objects; when you add a new element, it's stacked on top of the others. When you pull an element off the stack, it comes off the top. That element is removed from the stack completely, unlike a structure such as an array, where the elements are always available.
Scanner
import java.util.Scanner static Scanner userInput = new Scanner(System.in); public static void main() { ... if (userInput.hasNextInt()) {} }
Basic Calculator
import java.util.Scanner; public class BuildingABasicCalculator7 { public static void main(String[] args) { Scanner bucky = new Scanner(System.in); double fnum, snum, answer; System.out.println("Enter first num "); fnum = bucky.nextDouble(); System.out.println("\nEnter second num "); snum = bucky.nextDouble(); answer = fnum + snum; System.out.println("\nFnum and Snum added together equal"); System.out.println(answer); } }
User Input
import java.util.Scanner; public class GettingUserInput6 { public static void main(String args[]){ Scanner bucky = new Scanner(System.in); System.out.println(bucky.nextLine()); } }
Methods With Parameters- Class 1
import java.util.Scanner; public class UseMethodsWithParameters15 { public static void main(String[] args) { Scanner input = new Scanner(System.in); UseMethodsWithParameters15P2 UseMethodsWithParameters15P2Object = new UseMethodsWithParameters15P2(); System.out.println("Enter your name here: "); String name = input.nextLine(); UseMethodsWithParameters15P2Object.simpleMessage(name); } }
Importing a Class from a Package
import packageName.ClassName;
how to get error message
in catch statement catch(ArithmeticException e) {e.toString());} which gives the exception name + the description, while getMessage() only gives description
Graphics context
in java, an object associated with a component where the images for that component are drawn
method, which finds the index of an element based on the element itself:
indexOf("Inkster"); (example: int i = v.indexOf("Inkster"); )
\n
indicates a newline character
\t
indicates a tab character
pseudocode
informal programming language with english like constructs
variables declared inside a class but outside any method
instance variables
Statements
instructions or commands within a method that make a program work
machine language
instructions that can be executed directly by the CPU
How could you define an integer named num and initialize it to 394?
int num = 394;
Example of how to find out how many buts are being represented in a set:
int numBits = connex.size();
1. Define a variable that = to ten. 2. Create a while loop that prints you name tens time.
int ten = 10; while(copies > ten) { System.out.println("Reynald"); copies --; }
conditional operator
int var = expression ? value 1 : value 2; (true/false) (true) (false)
Name the 6 numeric data types
int, double, short, long, byte, and float
Numeric Data Sub-Types
int, long, float, double
Declare an array
int[] anArray;
1. Create an Array called 'number' w/ 3 slots 2. Write out the 2nd number
int[] numbers = new int[3];
IDE
integrated development environment. a programming environment that includes an editor, compiler, and debugger
public and abstract
interface methods are implicitly what?
Iterator
interface that provides a standard means of going through a list of elements in a defined sequence, which is a common task for many data structures.
Serialize
involves saving the current state of an object to a stream, and restoring an equivalent object from that stream. The stream functions as a container for the object.
literals
items in programs whose values do not change; restricted to the primitive data types and strings
Literals
items whose values do not change, like the number 5.0 or the string "Java"
reason for abstract classes in java
java does not allow multiple subclasses
more eagle-eyed view of exception types
java.util.RunTimeException (developer responsible for catching these) java.util.Exception (compiler will warn about these errors anyway) common Exceptions, which are the 5 above types
Return
keyword that stops execution of the method,goes back to where you started
What could a object be compared to for similarity?
like base blocks that are interchangeable in how they can be used in other programs.
statements
lines of code in java
variables declared inside a method or method parameter
local variables
Number of comparisons in binary search
log(n)
boolean operator
logical operator. && || !=
Infinite loop
loop that goes forever(while)
4. The -______- is where the program begins execution.
main Method
Helper methods should be
marked as private
hasNext()
method determines whether the structure contains any more elements.(if you've implemented the iterator interface)
contains()
method from hashtable class that checks whether an object is stored in the hash table.
public static void main(String [ ] args)
method header;
clone
method of Object. Creates and returns a copy of this object( Class Object).
next()
method retrieves the next element in a structure. (if you've implemented the iterator interface)
mutator method
method that changes the state of an object
Mutator methods
methods that change the values of the field
The two main kinds of methods:
methods that return a value / void methods
ArrayList methods
names.size() names.get(i); names.set(0, "Felicia Day"); this will REPLACE John Smith names.remove(3); copy: copiedAR.addAll(names); copy names ArrayList into copiedAR if (names.contains(paulYoung)) {} to check if two arrays are equal (containsAll elements of ) -- if (names.containAll(namesCopy)) {} //if the ArrayList names contains All elements in namesCopy .clear() .isEmpty() secondCopy = namesCopy.toArray(); //copy to secondCopy
<0
negative
Array Construction
new tymeName[length];
instantiation operator
new, third highest precedence, right to left association
/n
newline; advances the curson to the next line for subsequent printing
how is constructor definition different from a method
no return type...constructor includes access modifier, which is usually public, but can also (surprisingly) be private or default(no access modifier at all (?))
is private variable accessible within inherited subclass
no...access violation...and reason for accessor methods
Comments
nonexecutable statements in a program that can be used to document the purpose of the program or to track changes to the program
!=
not equal
!
not(makes true or false)
Primitive data types
numbers, characters, and Booleans. combined in expression with operators
Method call
object.methodName(parameters);
When using the BitSet class "0" represents ______
off or false(boolean)
When using the BitSet class "1" represents ______
on or true(boolean)
Method
one or more statements in a class performing a specific task within an object
/** */
opening comments
{ }
opening/closing braces; encloses a group of statements, such as the contents of a class or a method
( )
opening/closing parentheses; used in a method header
||
or(one or both are true)
explicit parameter
parameter of a method OTHER THAN THE OBJECT ON WHICH METHOD IS INVOKED
logic gate
performs a logical operation on one or more logic inputs and produces a single logic output
Decision Construct
permits program to make logical decisions and choose between alternate execution paths
>0
positive
System.out.println( _____ );
prints the content in the parentheses ( _____ ) and moves to the next line
System.out.print( _____ );
prints the content in the parentheses ( _____) and remains on the same line
private accessor: security vs freedom
private often cited as giving SECURITY...but most often, it gives freedom to change instance fields
class and package access modifiers
public - member accessible within and outside package private - member accessible only to other members within class (NOT subclass!) protected - accessible within package and all of its subclasses (including subclasses in other packages)
default access modifier, type for variables within interfaces
public abstract
How to define a class?
public class "class name" (no extension)
If Statement
public class IfStatement10 { public static void main(String[] args) { int test = 6; if (test == 9){ System.out.print("yes"); }else{ System.out.println("this is else"); } } }
Increment Operator
public class IncrementOperators9 { public static void main(String[] args) { int tuna = 5; int bass = 18; ++tuna; System.out.println("Tuna- " + tuna); System.out.println("Bass- " + bass++); int x; x = 5; x += 5; System.out.println("this is x- " + x); int y; y = 2; y *= 5; System.out.println("this is y- " + y); } }
Logical Operator
public class LogicalOperators11 { public static void main(String[] args) { int boy, girl; boy = 18; girl = 68; // && both have to be true, || one has to be true if (boy > 10 && girl < 60){ System.out.println("You can enter"); }else{ System.out.println("You can not enter"); } } }
Math Operators
public class MathOperators8 { public static void main(String[] args) { int girls,boys,people; girls = 11; boys = 3; people = girls % boys; System.out.println(people); } }
Switch Statement
public class SwitchStatement12 { public static void main(String[] args) { int age; age = 30; switch (age){ case 1: System.out.println("you can crawl"); break; case 2: System.out.println("you can talk"); break; case 3: System.out.println("you can get in trouble"); break; default: System.out.println("I dont know how old you are"); break; } } }
Methods With Parameters- Class 2
public class UseMethodsWithParameters15P2 { public void simpleMessage(String name) { System.out.println("Hello " + name); } }
Multiple Classes- Class 1
public class UsingMultipleClasses14 { public static void main(String[] args) { UsingMultipleClasses14Part2 MultipleClasses2Object = new UsingMultipleClasses14Part2(); MultipleClasses2Object.simpleMessage(); } }
Multiple Classes- Class 2
public class UsingMultipleClasses14Part2 { public void simpleMessage(){ System.out.println("This is another class"); } }
Variables
public class Variables5 { public static void main(String args[]){ double tuna; tuna = 5.28; System.out.print("I want "); System.out.print(tuna); System.out.println(" movies"); } }
define new class Vehicle that implements Drivable interface
public class Vehicle implements Drivable
While Loop
public class WhileLoop13 { public static void main(String[] args) { int counter = 0; while (counter < 10){ System.out.println(counter); counter++; } } }
use of throws
public static void getAFile(String filename) throws IOException, FileNotFoundException{ FileInputStream file = new FileInputStream(filename); } and above in the main method, will set up try/catch blocks for suspect code
the entry point for your application
public static void main(String [] args)
Standard Starting, to start code block?
public static void main(String[] args) { //code goes here }
Given this method below, implements 'continue' or 'break' statement if color is 'green' public void printColors() { String[] colors = new String[] {"red","blue", "green","yellow"}; for (String c : colors) { System.out.println(c); } }
public void printColors() { String[] colors = new String[] {"red","blue", "green","yellow"}; for (String c : colors) { if("green".equals(c)) continue; System.out.println(c); } }
" "
quotation marks; encloses a string of characters, such as a message that is to be printed on the screen
IS-A relationship
relationship to describe extends
HAS-A relationship
relationship to describe instance variables
removes an element based on the element itself rather than on an index:
removeElement("Inkster");
console.nextDouble():
retrieves that floating-point number, if the value of this expression is that floating-point number.
The return Statement
return expression;
/r
return; causes the cursor to go to the beginning of the current line, not the next line
syntax
rules that define how to form instructions in a particular programming language
objects
second category of Java variables such as scanners and strings
;
semicolon; marks the end of a complete programming statement
Objects
sent messages
loop
sequence of instructions that is executed repeatedly
method
sequence of statements with a name. may have formal parameter and may return a value.
instruction set
set of all operations that can be executed by a processor
Mutators
set() methods
What is the method signature of public void setDate(int month, int day);?
setDate(int, int);
Naming standard for mutator method?
setXYZ();
programming vs natural languages
size, rigidity, literalness
I/O buffer
small amount of memory inside the I/O controller
I/O controller
special purpose computer that handles details of input and output and compensates for speed difference between I/O devices and other parts of the computer.
Parameter passing
specifying expressions to be actual parameter values for a method when it is called
Class/Static Method
static keyword
mass storage
storage of large amount of data in machine readable form for access by a computer system
computer science
study of algorithms including their: mathematical and formal properties, hardware realizations, linguistic realizations, and application
subclass extends the superclass
superclass / subclass relationship in java
int x = (int)a;
syntax to cast type (double a = 1.54;) into an int
public Class Dog extends Animal implements Pet{}
syntax to create an Animal subclass called dog that has a pet interface
super.runReport();
syntax to run superclass' runReport() method
Loop
tells java do things over and over
Cache Memory
temporary storage area where frequently accessed data can be stored for rapid access. fast, expensive, small. First site of search.
if-else construct
tests value of var/expr
The capacity of a vector is:
the amount of memory allocated to hold elements, and it is always greater than or equal to the size.
Uppercase
the capital letters of the alphabet
Stored Program concept
the computers ability to store program instructions as binary in main memory for execution. Created by von Neumann
Object
the instance of a class containing data and the functions that manipulate the data
address
the memory address of the values of which an operation will work
Lowercase
the non capital letters of the alphabet
The size of a vector is:
the number of elements currently stored in it.
implicit parameter
the object on which a method is invoked. comes before the method. myAccount.getDeposit(). my account is the implicit parameter
Scope
the part of a program in which the variable is defined
Origin
the point (0,0) in a coordinate system
Main method
the primary method in a java application program
syntax
the rules for combining words into sentences
vocabulary
the set of all of the words and symbols in a given language
literal
the source code representation of a fixed value
A parameter is a local variable initialized to....
the value of the corresponding argument. (Known as Call-by-value)
von neumann architecture
theoretic model of computer design that structures the origin of all modern computers. four subsystems: memory, in/output, ALU, control unit.
What is the biggest limitation to using arrays?
they cant adjust in size to accommodate greater or fewer elements.
ObjectInputStream
this class deserializes primitive data and objects previously written using an ObjectOutputStream. ObjectOutputStream and this class can provide an application with persistent storage for graphs of objects when used with a FileOutputStream and FileInputStream respectively. this class is used to recover those objects previously serialized. Other uses include passing objects between hosts using a socket stream or for marshaling and unmarshaling arguments and parameters in a remote communication system.
using this(newHealth) within constructor
this goes up to the root class (Monster) and newHealth refers to it's field (class variable)
5. The -______- always returns a reference to a String that contains the state of the object.
toString Method
primitive data type
total of 8, include 4 integer types and 2 floating point types. int 4, byte 1, short 2, long 8, double 8, float 4, char 2, boolean 1 bit. A value that's not a reference to an object.
stack and heap
two main memory locations for Java
super keyword in Java
two uses 1) call a superclass constructor (since superclass/subclass constructors seem to be confusing business) 2) access a member of the superclass that has been hidden by a member of a subclass
Variable definition
typeName variableName = value;
how to prevent overriding or inheritance
use of final before class declaration
Escape character (\)
used in codes to represent characters that cannot be directly typed into a program
escape character
used when including 'special characters' in string literals
Array Manipulations
useful operations provided by methods in the java.util.Arrays class, are: Searching an array for a specific value to get the index at which it is placed (the binarySearch method). Comparing two arrays to determine if they are equal or not (the equals method). Filling an array to place a specific value at each index (the fill method). Sorting an array into ascending order. This can be done either sequentially, using the sort method, or concurrently, using the parallelSort method introduced in Java SE 8. Parallel sorting of large arrays on multiprocessor systems is faster than sequential array sorting.
BitSet class
useful when you need to represent a large amount of binary data, bit values that can be equal only to 0 or 1. These also are called on-or-off values
Example of how to add a element to a vector:
v.add("Inkster");
How would you wipe out all of a the elements inside of a vector named "v"
v.clear();
Example of how to remove items from a vector:
v.remove(3);
example of how to change a specific element :
v.set(1, "Kung");
formal parameter
variable in a method definition. initialized with an actual parameter when method is called.
final
variable is defined with the reserved word its value can never change. Ex: final double .canVolume = 0.335;
local variable
variable whose scope is a block
Assignment
variableName = value;
Constants
variables whose values cannot change
romantics
very invested in cult of genius...write about michalangelo....seems to be pront to depression...forgets to take off boots... modern notion of genius invested in notion of intellectual originality...copyright law
instance variables and methods
what are members of a class?
type name in angle brackets
what is a type parameter
when you don't want a class to be instantiated
what is an abstract class?
a reference variable of the object type linked together by the = operator
what is an object
changing an inherited method
what is overriding
package name + class name
what is the full class name
abstract and non-abstract
what kind of methods are allowed in an abstract class
default
what to do if not listed case
run-time errors
when a computer is asked to do something that is considered illegal
variable declaration statement
when a program declares the type of a variable
syntax errors
when a syntax rule is violated
scope
when a variable can be accessed in the same block
logic errors
when the computer is unable to express an answer accruately
When is the BitSet class useful?
when you need to keep up with a set of Boolean values; you simply assign a bit to each value and set or clear it as appropriate.
on the stack inside the frame corresponding to the method where the methods were declared
where do all local variables live?
The while Statement
while (condition) statement;
socrates daemon
whispered the language of the gods into his ear before he did something incorrect vessel genies harnessed by divine madness infused by the goes that whips the individual into ecstatic states and pushes them into writing great things aristotle infused before birth == the problems -- written by student -- why is it that individuals of great capacity seem to be subject to melancholy? sanguine? extradorinary indiviuals have similary physiology ...side effects...maddness...irrationality its sad to think of how many geniuses have died on the african veldt
setup a constructor
within Monster class, create public Monster(int newHealth, int newAttack, int newMovement) {}
local vs instance variables
within a method(so w/in method's stack frame) vs not...a constructor IS NOT a method... instance variables live on the heap and are best set as parameters to the constructor in a single call...thus constructing object and its variable (initializing object's state) in one call
keywords
words in java that cannot be used as user-defined symbols
import x.y.z
x - overall name of package, y - name of package subsection, z - name of particular class in subsection
What is this "x+=3" the equivalent of?
x = x + 3;
compound assignments
x+=1
difference between while loop and do while loop
x=10 do { System.out.println("X is equal to " +x); x++; } while (x<10) This will return "X is equal to 10", while while loop would not return any thing at all. (Do-while returns initialization, regardless of whether it meets while condition).
Block statement
{ statement; statement; }
What must every method and class have an open and closed of?
{ } (braces, or curly brackets)
Array
~An ordered set of values of the same time stored in CONTIGUOUS blocks of memory ~non-primitive
Array subscripts
~Anything that evaluates to integer value ~Begin with 0 ~Cannot be negative ~Should not be referenced beyond bounds
Scanner Class
~Scans input from various sources and returns representations of primitive types
String
~Set of characters that are treated as objects ~Are immutable
ArrayList
~Subclass of Collection ~Works like an array, but SIZE can be EXPANDED easily. Very efficient for random accessing, but not so for inserting in the middle.
Reading from Text Files
~Uses Reader class ~BufferedReader: Provides buffered text stream reading ~FileReader: Connects an input stream to file
Writing to Text Files
~Uses Writer class ~BufferedWriter: Writes text to text output streams and provides buffering ~PrintWriter: Uses methods to write formatted data to output streams ~FileWriter: connects an output stream to a file
ArrayList Methods
~add(object): adds to end of list ~add(index, object) ~set(index, object) - replaces ~get(index) ~remove(index) size() isEmpty() - boolean clear() - removes all elements
String Class Methods
~length() ~substring(starting pos(, ending pos)) ~toUpperCase(), toLowerCase() ~charAt() ~equals()
Scanner methods
~nextInt(),....,nextLine() ~next(): returns next token ~hasNext(): boolean: returns true if source is full; false if empty
PrintWriter Methods
~print(arg) ~println(arg)
