Transcript Intro to Java 2

Intro to Java 2
By Geb Thomas
Based on the Java Tutorial
What is Java?
Platform independent code
Runs on many machines
Runs within browsers as applets
Will 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
Classes
Definition: A class is a blueprint, or prototype, that defines the variables
and the methods common to all objects of a certain kind.
Inheritance
Subclass
Superclass
Hierarchy
Inheritance
Override
Abstract classes
Putting the Ideas Into Action
ClickMe.java
Spot.java
<applet code="ClickMe.class"
width="300" height="150"> </applet>
First Swing Example
import 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)
User presses a mouse button while the cursor is
over a component
User moves the mouse over a component
Component becomes visible
Component gets the keyboard focus
Table or list selection changes
WindowListener
MouseListener
MouseMotionListen
er
ComponentListener
FocusListener
ListSelectionListene
r