Java SE (Java Platform, Standard Edition)

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class Focus extends Applet implements KeyListener {
	Button button;
	TextField field;
	public void init() {
		button = new Button("Push Me");
		field = new TextField("Type me");
		button.addKeyListener(this);
		field.addKeyListener(this);
		add(button);
		add(field);
	}
	public void keyPressed(KeyEvent e) {
		if (e.getKeyCode() == KeyEvent.VK_TAB) {
			Component comp = (Component)e.getSource();
			comp.transferFocus();
		}
	}
	public void keyReleased(KeyEvent e) {}
	public void keyTyped(KeyEvent e) {}
}

public class Client extends JApplet {
    public Client() {
        MyTopPanel myTopPanel = new MyTopPanel();
        this.getContentPane().add(myTopPanel);
    }
}

public class MyTopPanel extends JPanel {
    public MyTopPanel() {
         LeftPanel leftPanel = new LeftPanel();
         CenterPanel centerPanel = new CenterPanel();
         this.add(leftPanel,BorderLayout.WEST);
         this.add(centerPanel,BorderLayout.CENTER);
    }
}

public class CenterPanel extends JPanel {
    public CenterPanel() {
        JTextField test = new JTextField(10);
        test.requestFocus();
        this.add(test);
        JTextField second = new JTextField(10);
        this.add(second);
    }
}