Sample Code from "Java How to Program, Fifth Edition" from Deitel and Deitel.

The following code gives to an example of a simple Java program.

Notice that the whole thing is a class, within it is a main function

Be sure to name your file the same as the class name

Compile with "javac Wecome1.java"

Run with "java Welcome1"

Another simple printing program with "print"

Compile and run as above except use "Welcome2"

Using "\n"

Graphical User Interface (GUI) example

Notice that we are making use of a predefined java class "JOptionPane", therefore, we "import javax.swing.JOptionPane"

Graphical User Interface (GUI) getting user input (showInputDialog) and printing out a message (showMessageDialog).

Comparisons in Java

• embedded in a HyperText Markup Language (HTML) document
• when browser loads a web page with an an applet, the applet downloads into the Web browser and begins execution

Basic "Welcome to Java Applet". Notice:

• importing: "java.awt.Graphics" so that we can draw (work with Graphics)
• importing: "javax.swing.JApplet" so that we can inherit from the basic JAapplet class
• "WelcomeApplet extends JApplet". This is java's way of doing inheritance. Our WelcomeApplet will inherit from JApplet.
• Applet container calls three methods when beginning execution:
  1. init
  2. start
  3. paint
• WelcomeApplet overrides (redefines) the super class version of paint

Also need an html file:

Compile with "javac WelcomeApplet.java"

Run by opening .html file in browser or

"appletviewer WelcomeApplet.html

Drawing two strings at different locations.

x and y coordinates are (0,0) in the upper left-hand corner

Drawing lines

Drawing rectangles and getting input from user. Notice overriding "init" function. This does the initialization of two numbers.

"paint" draws the results.