Chapter 4-6 (Exam 2)
Logical NOT
! (unary, boolean) reverses the truth of an expression
Logical AND
&& (binary, boolean) will evaluate to false as soon as it sees that one of its operands is a false expression
Objects
(a) can store data, fields (b) can perform operations, methods
public
+
private
-
Reading from a file
1. import java.io.*; 2. main -> throws IOException 3. File file= new File(filename); Scanner inputFile = new Scanner(file); 4. String line = inputFile.nextLine(); 5. inputFile.close();
Writing to a file
1. import java.io.*; 2. main -> throws IOException 3. PrintWriter outputFile = new PrintWriter(filename); 4. outputFile.println(friendname); 5. outputFile.close();
Decimal Format
1. import java.text.DecimalFormat; 2. DecimalFormat dollar = new DecimalFormat("#,##0.00); 3.dollar.format(totalSales);
In your textbook the general layout of a UML diagram is a box that is divided into three sections. The top section has the _______; the middle section holds _______; the bottom section holds _______. a. class name; attributes or fields; methods b. class name; object name; methods c. object name; methods; attributes or fields d. object name; class name; methods
A
Which of the following will open a file named MyFile.txt and allow you to append data to its existing contents? a. FileWriter fwriter = new FileWriter("MyFile.txt", true); PrintWriter outFile = new PrintWriter(fwriter); b. PrintWriter pwriter = new PrintWriter("MyFile.txt"); FileWriter outFile = new FileWriter(pwriter); c. PrintWriter outfile = new PrintWriter("MyFile.txt", true); d. PrintWriter outfile = new PrintWriter(true, "MyFile.txt"); e. None of these
A
When an object is passed as an argument to a method, what is passed into the method's parameter variable? a. the class name b. the object's memory address c. the values for each field d. the method names e. None of these
B
Local variables a. are hidden from other methods b. may have the same name as local variables in other methods c. lose the values stored in them between calls to the method in which the variable is declared d. All of the above e. None of a. , b. or c.
D
Which of the following are classes from the Java API? a. Scanner b. Random c. PrintWriter d. All of the above e. Only a. and b.
D
Which of the following is not a benefit derived from using methods in programming? a. problems are more easily solved b. simplifies programs c. code reuse d. all of the above are benefits e. Only a. and b.
D
A UML diagram does not contain: a. the class name. b. the method names. c. the field names. d. access modifiers e. object names
E
T/F A method in a class declared as static may be invoked by a client simply by using the name of the method alone.
False
T/F In the method header, the method modifier public means that the method belongs to the class, not a specific object.
False
T/F When the break statement is encountered in a loop, all the statements in the body of the loop that appear after it are ignored, and the loop prepares for the next iteration.
False
Reading data from a File
File myFile = new File("Costumers.txt"); Scanner inputFile = new Scanner(myFile);
T/F An argument passed by value to a method could be a constant, a variable, or an expression.
True
UML
Unified Modeling Language
Access Specifier
a Java keyword that indicates how a field or method can be accessed
Flags
a boolean variable that monitors some condition in a program
Class
a code that describes a particular type of object
no-arg constructor
a constructor that does not accept arguments
shadowing
a method may have a local variable with the same name as an instance field
constructor
a method that is automatically called when an object is created
The if-else statement
adds the ability to conditionally execute code when the if condition is false
The switch statement
allows you to use an ordinal value to determine how a program will branch
hasNext()
boolean method will return turn if another item can be read from the file
The break Statement
can be used to abnormally terminate a loop **not recommended
Sentinel value
can be used to notify the program to stop acquiring input (a non-possible value)
Comparing characters
characters are ordinal
static
class method
stale data
data that requires the calculation of various factors has this potential risk
The if statement
decides whether a section of code executes or not
Calling a method
displayMessage();
Comparing String objects
equals or compareTo methods (are both case sensitive)
Nested if statements
if statement appears inside another if statement
Strings are ___________________
immutable
Writing text to a File
import java.io*; PrintWriter outputFile = new PrintWriter("StudentData.txt"); outputFile.print(";lkasj;flkajs;"); outputFile.println(";laksdjfa;oi");
Random Class
import java.util.Random; Random randomNumbers =new Random();
y++
indicates that the variable will be incremented or decremented after the rest of the equation has been evaluated
--y
indicates that the variable will be incremented or decremented prior to the rest of the equation being evaluated
The if-else-if statements
makes certain types of nested decision logic simpler to write; else statements match up with the immediately preceding unmatched if statement
method signature
method name and parameter data types *NOT the return type
mutators
methods that modify the data of fields
accessors
methods that retrieve the data of fields
instance
object created from a class
void method
one that simply performs a task and then terminates
java.lang
package automatically available to any Java class
references are______________________
passed by address
arguments are _____________________
passed by value
value-returning method
performs a task and then sends a value back to the code that called it
The do-while loop
post-test loop use it where you want the statements to execute at least one time
The for loop
pretest loop use it where there is some type of counting variable that can be evaluated
The while loop
pretest loop use it where you do not want the statement to execute if the condition is false in the beginning
Method header
public static void displayMessage()
Conditional operator
ternary operator works like an if else statement BooleanExpression ? value 1: value 2
DecimalFormat Class
the full fractional value of doubles and floats will be printed
Input validation
the process of ensuring that user input is valid
binding
the process of matching a method call with the correct method
The printf method
to perform formatted console output System.out.printf(FormatString, ArgList)
overloading
two or more methods or constructors in a class that have the same name but different parameter lists
methods
used to break a problem down into small manageable pieces
Exception
when something unexpected happens in a Java program this is thrown
The continue Statement
will cause the currently executing iteration of a loop to terminate and the next iteration will begin
Increment and decrement operators
y++ --y
Logical OR
|| (binary, boolean) will evaluate to true as soon as it sees that one of its operands is a true expression