©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Ch2: Getting Started with Java - Objectives After you have read and studied this chapter, you should be able to Identify the basic components of Java programs Write simple Java programs Describe the difference between object declaration and creation Describe the process of creating and running Java programs Use the Date, SimpleDateFormat, String, and JOptionPane standard classes Develop Java programs, using the incremental development approach

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Program Ch2Sample1 import javax.swing.*; class Ch2Sample1 { public static void main(String[ ] args) { JFramemyWindow; myWindow = new JFrame( ); myWindow.setSize(300, 200); myWindow.setTitle(“My First Java Program”); myWindow.setVisible(true); } Declare a name Create an object Use an object

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Program Diagram for Ch2Sample1 myWindow : JFrame Ch2Sample1 setSize(300, 200) setTitle(“My First Java Program”) setVisible(true) myWindow : JFrame Ch2Sample1 Dependency Relationship

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Object Declaration and Creation JFrame myWindow; myWindow = new JFrame ( ) ; Declaration vs. Creation? Sending a message Program Components –comments, –import statements, and –class declarations.

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Why Use Standard Classes Don’t reinvent the wheel. When there are existing objects that satisfy our needs, use them. We will introduce four standard classes here: –JOptionPane : showMessageDialog(…), –String : substring(), length(), indexOf() –Date –SimpleDateFormat.

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter name String is an Object 1. The identifier name is declared and space is allocated in memory. 2. A String object is created and the identifier name is set to refer to it String name; name = new String(“Jon Java”); : String Jon Java name 2

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Examples: substring String text = “Espresso”; text.substring(6,8) text.substring(0,8) text.substring(1,5) text.substring(3,3) text.substring(4,2) “so” “Espresso” “spre” error “”

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Examples: length String str1, str2, str3, str4; str1 = “Hello” ; str2 = “Java” ; str3 = “” ; //empty string str4 = “ “ ; //one space str1.length( ) str2.length( ) str3.length( ) str4.length( )

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Examples: indexOf String str; str = “I Love Java and Java loves me.” ; str.indexOf( “J” ) str2.indexOf( “love” ) str3. indexOf( “ove” ) str4. indexOf( “Me” )

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Examples: concatenation String str1, str2; str1 = “Jon” ; str2 = “Java” ; str1 + str2 str1 + “ “ + str2 str2 + “, “ + str1 “Are you “ + str1 + “?” “JonJava” “Java, Jon” “Are you Jon?”

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Date The Date class from the java.util package is used to represent a date. When a Date object is created, it is set to today (the current date set in the computer) The class has toString method that converts the internal format to a string. SimpleDateFormat: for formatting date options JOptionPane for Input: String name; name = JOptionPane.showInputDialog (null, “What is your name?”);

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Problem Statement Problem statement: Write a program that asks for the user’s first, middle, and last names and replies with their initials. Example: input: Andrew Lloyd Weber output: ALW

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Overall Plan Identify the major tasks the program has to perform. Tasks: –Get the user’s first, middle, and last names –Extract the initials and create the monogram –Output the monogram This is given in the textbook. Let us do an in-class demo of a program titled “ Parser.java”.