Intro to Java 2 By Geb Thomas Based on the Java TutorialJava Tutorial

Intro to Java 2

By Geb ThomasBased on the Java Tutorial

What is Java?Platform independent codeRuns on many machinesRuns within browsers as appletsWill soon run on cell phones, microwaves, car displays and washing machines, for example.

How do you make Java go?Create a java file (HelloWorldApp.java)Compile the java file with javac to make bytecodes (javac HelloWorldApp.java)

Creates HelloWorldApp.class

Run the bytecodes on a java virtual machine. (java HelloWorldApp)

Where Do You Get This Stuff?

http://java.sun.com

A Simple Example

/** The HelloWorldApp class implements an application that * simply displays "Hello World!" to the standard output. */

class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!"); //Display the string. }}

Objects

Objects are high level concepts that can have

Variables (data associated with the concept)Methods (actions associated with the concept)

Passing Messages

ClassesDefinition: A class is a blueprint, or prototype, that defines the variables and the methods common to all objects of a certain kind.

InheritanceSubclassSuperclassHierarchyInheritanceOverrideAbstract classes

Putting the Ideas Into Action

ClickMe.java Spot.java <applet code="ClickMe.class" width="300" height="150"> </applet>

First Swing Exampleimport javax.swing.*;

public class HelloWorldSwing { public static void main(String[] args) { JFrame frame = new JFrame("HelloWorldSwing"); final JLabel label = new JLabel("Hello World"); frame.getContentPane().add(label); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.pack(); frame.setVisible(true); } }

Actions and Events

Examples of Events and Their Associated Event Listeners

Act that Results in the Event Listener Type

User clicks a button, presses Return while typing in a text field, or chooses a menu item

ActionListener

User closes a frame (main window) WindowListener User presses a mouse button while the cursor is over a component

MouseListener

User moves the mouse over a component MouseMotionListener Component becomes visible ComponentListener Component gets the keyboard focus FocusListener

Table or list selection changes ListSelectionListener