© 2007 Lawrenceville Press Slide 1 Chapter 3 Classes and Objects 1. How is a class different from an object?

© 2007 Lawrenceville Press Slide 2 Chapter 3 A Java Application /** * The Greeting class displays a greeting */ public class Greeting { public static void main(String[] args) { System.out.println("Hello,world!"); } comment class declaration method statement

© 2007 Lawrenceville Press Slide 3 2. Write the class declaration for a class named Farewell with a method named sayGoodbye with a statement that prints the word “bye” with a comment that contains your name

© 2007 Lawrenceville Press Slide 4 Chapter 3 Executing a Java Application public class Greeting public static void System.out.printl } source code 03 3b ff f abytecode... c cilbup Hello,world! b3 30 compiler JVM

© 2007 Lawrenceville Press Slide 5 Chapter 3 Escape Sequences An escape sequence is a backslash ( \ ) followed by a symbol that together represent a character. Commonly used escape sequences: \n newline \t tab (8 spaces) \\ backslash \" double quotation mark

© 2007 Lawrenceville Press Slide 6 Chapter 3 The format() Method  A method in the System class  Used to control the way output is displayed  Requires a format string and an argument list  The format string specifier takes the form: %[alignment][width]s  For example System.out.format("%-6s %4s", "Test1", "90"); displays: Test1 90

© 2007 Lawrenceville Press Slide 7 Chapter 3 Code Conventions  An introductory comment should begin a program.  Package names should begin with a lowercase letter and then an uppercase letter should begin each word within the name.  Class names should be nouns and begin with an uppercase letter and an uppercase letter should begin each word within the name.  A comment block should be included before each class.

© 2007 Lawrenceville Press Slide 8 Chapter 3 Code Conventions (con't)  Comments should not reiterate what is clear from the code.  Statements in a method should be indented.  An open curly brace ( { ) should be placed on the same line as the class or method declaration, and the closing curly brace ( } ) should be on a separate line and aligned with the class or method declaration.

© 2007 Lawrenceville Press Slide 9 Chapter 3 Flowchart Symbols input/output start/end

© 2007 Lawrenceville Press Slide 10 Chapter 3 The Triangle Flowchart