Window Maximization

Answer:
The Java AWT does not provide an interface for maximizing a window. The Swing JInternalFrame supports a setMaximum() method that will maximize an internal frame, but that only works when your all your windows are contained within a JFrame. Frames, Windows, and JFrames cannot be maximized with a simple method call. You can work around this limitation by querying the system for the screen size and explicitly setting the size of the window.

The only problem is that after you include the native window system's borders and title bar, the window may exceed the size of the screen. Some window systems will not allow this and automatically resize the window to completely fit the screen. When you maximize a window in this manner, you will want to save the original dimensions of the window so you can restore them later. The following program demonstrates how to do this. It creates a Frame containing a button that will maximize or restore the window size when pressed.

import java.awt.*;
import java.awt.event.*;

/**
 * Creates a window with a button that will maximize or restore the
 * size of the window when pressed.
 */
public class Maximize extends Frame {
  boolean _isMaximized = false;
  int _oldWidth, _oldHeight;
  Button _button;

  public Maximize() {
    _button = new Button("Maximize");
    add(_button, BorderLayout.CENTER);

    _button.addActionListener(new ActionListener() {
	public void actionPerformed(ActionEvent e) {
	  Toolkit toolkit = Toolkit.getDefaultToolkit();

	  if(!_isMaximized) {
	    Dimension screenSize = toolkit.getScreenSize();
	    _oldWidth  = getWidth();
	    _oldHeight = getHeight();
	    setSize(screenSize.width, screenSize.height);
	    _button.setLabel("Restore");
	  } else {
	    _button.setLabel("Maximize");
	    setSize(_oldWidth, _oldHeight);
	  }

	  _isMaximized = !_isMaximized;
	}
      });
  }

  public static final void main(String[] args) {
    Frame frame;
    WindowListener exitListener;

    frame  = new Maximize();

    exitListener = new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        Window window = e.getWindow();
        window.setVisible(false);
        window.dispose();
        System.exit(0);
      }
    };

    frame.addWindowListener(exitListener);
    frame.pack();
    frame.setVisible(true);
  }
}