The Program Explained

Here is the program again:

import java.awt.*; // import the abstract windowing toolkit
import javax.swing.*; // import the Swing classes

public class TestFrame1
{
  // usual application main
  public static void main ( String[] args ) 
  {
    JFrame frame 
        = new JFrame("Test Frame 1"); // construct a JFrame object
    frame.setSize(200,100);   // set it to 20 pixels wide by 100 high
    frame.setVisible( true ); // ask it to become visible on the screen
  }
}

The frame object created by new JFrame() is a section of main storage in your computer. It contains lots of information about what should appear on the monitor. But nothing will appear on the monitor without some additional work.

1. The AWT is imported since that is where many classes defined.
• This program does not need to do this, but usually you do.
2. The Swing package is imported since that is where JFrame is defined.
• You must do this.
3. A JFrame object is constructed.
4. The reference variable frame refers to the JFrame object.
5. The object's setSize() method sets its size.
6. The object's setVisible() method makes it appear on the screen.