Creating Java Program Ch1

Polymorphism

-"many forms" -Allows the same word to be interpreted correctly in different situations based on context

Finding help: Java Development Kit (JDK)

-A software development kit (SDK) of programming tools -Free to download

Adding comments to a java class (Javadoc comments):

-A special case of block comments -Begin with a slash and two asterisks (/**) -End with an asterisk and a forward slash (*/) -Use to generate documentation

Finding help: Java API

-Also called the Java class library -Provides prewritten information about Java classes

Attributes

-Characteristics that define an object -Differentiate objects of the same class -The value of attributes is an object's state

Java interpreter

-Checks byte code and communicates with the operating system. -Executes byte code instructions line by line within the JVM

Compiling a Java class

-Compile the source code into bytecode -Translate the bytecode into executable statements (using a Java interpreter) -Type javac First.java

Object-oriented programming was used most frequently for two major types of applications:

-Computer simulations -GUI (graphical user interfaces) [not all object oriented programs are written to use a GUI]

Encapsulation

-Conceals internal values and methods from outside sources -provides security -keeps data and methods safe from inadvertent changes

Class

-Describes objects with common properties -A definition -An instance

Dont do it:

-Don't forget the file's name must match the class name -Don't confuse these terms: -Parentheses, braces, brackets, curly braces, square brackets, and angle brackets -Don't forget to end a block comment -Don't forget that Java is case sensitive -Don't forget to end every statement with a semicolon -Do not end class or method headers with a semicolon -Don't forgot to recompile when making changes -Don't panic when you see a lot of compiler error messages -Don't assume your program is perfect when all compiler errors are eliminated

Java app that produces GUI output

-JOptionPane: Produces dialog boxes -Dialog box: A GUI object resembling a window. Messages placed for display -import statement: Use to access a built-in Java class -Package: A group of classes

correcting logic errors

-Logic error: The syntax is correct but incorrect results were produced when executed -Run-time error: Not detected until execution. Often difficult to find and resolve

java class: reasons for error messages

-Misspelled the command javac -A misspelled filename -Not within the correct subfolder or subdirectory on the command line -Improper installation of Java

Modifying a compiled java class

-Modify the text file that contains the existing class -Save the file with changes using the same filename -Compile the class with the javac command -Interpret the class bytecode and execute the class using the java command

Adding Comments to a Java Class (Program comments):

-Nonexecuting statements added to a program for documentation -Use to leave notes for yourself or others -Include the author, date, and class's name or function

Object-oriented programming differs from traditional procedural programming because of....

-Polymorphism -inheritance -Encapsulation

Running a java application

-Run the application from the command line (Type java First) -Shows the application's output in the command window -The class is stored in a folder named Java on the C drive

Saving a Java class

-Save the class in a file with exactly the same name and .java extension -For public classes, class name and filename must match exactly

Program statements

-Similar to English sentences -Commands that carry out program tasks

Adding comments to a java class (block comments):

-Start with a forward slash and an asterisk (/*) -End with an asterisk and a forward slash (*/)

Adding comments to a java class (line comments):

-Start with two forward slashes (//) -Continue to the end of the current line -Do not require an ending symbol

Correcting syntax errors (compile time error)

-The compiler detects a violation of language rules -Refuses to translate the class to machine code

Correcting syntax errors (first line of error message):

-The name of the file where the error was found -The line number -The nature of the error

Correcting syntax errors (next lines identify):

-The symbol -The location

Adding Comments to a Java Class (Comment out):

-Turn it into a comment -The compiler does not translate, and the JVM does not execute its command

Indent style

-Use whitespace to organize code and improve readability -For every opening curly brace ( { ) in a Java program, there must be a corresponding closing curly brace ( } ) -Placement of the opening and closing curly braces is not important to the compiler -Allman style used in text

Literal string

-Will appear in output exactly as entered -Written between double quotation marks

Inheritance

-an important feature of object-oriented programs -helps you understand real-world objects -classes share attributes and methods of existing classes but with more specific features

Java

-developed by Sun Microsystems -object oriented language -general purpose

Compilation outcomes

-javac is an unrecognized command -Program language error messages -No messages indicating successful completion

windows applications examples;

-menus -toolbars -dialog boxes

syntax error

-misuse of language rules -misspelled programming language word

Java advantages:

-security features -architecturally neutral -can be run on a wide variety of computer -doesnt execute instructions on the computer directly -runs on hypothetical computer known as JVM (Java Virtual Machine)

logic errors

-semantic errors -incorrect or procedures -program may run but provide inaccurate output

Bytecode

-statements saved in a file -a binary program into which the java compiler converts source code

Correcting syntax errors (Parsing)

Compiler divides source code into meaningful portions

Access specifier

Defines how a class can be accessed

Upper Camel casing (Pascal casing)

Each word of an identifier begins with uppercase letter: -UnderGradStudent -InventoryItem

High-level programming language

Let's you use a vocabulary of reasonable terms

Machine Language

Low-level programming language

Finding help: FAQs

On the Java Web site

Procedural programming

Operations executed in sequence

Arguments

Pieces of information passed to a method

System class

Refers to the standard output device for a system

method

Requires information to perform its task

Syntax

Specific rules for the language

Objects

Specific, concrete instances of a class (examples of the class)

main( ) method

Static: -A reserved keyword -Means the method is accessible and usable even though no objects of the class exist Void: -Use in the main( ) method header -Does not indicate the main( ) method is empty -Indicates the main( ) method does not return a value when called -Does not mean that main( ) doesn't produce output

Compiler/Interpreter

Translates a language into machine code

WORA

Write once, run anywhere

Computer program

Written intrusions that tells the computer what to do.

Method

a self-contained block of program code that carries out an action...similar to a procedure

Debugging

freeing the program of all errors

procedures

individual operations grouped into logical units

variables

named computer memory locations that hold value

Source code

programming statements written in high level programming language

Develpomental environment

set of tools used to write programs

Console applications

support character output