public class GermanTextField extends JTextField implements KeyListener{
  public GermanTextField() {
    init();
  }

  // other constructors ...

  private void init() {
    addKeyListener(this);
  }



  public void keyPressed(KeyEvent arg0) {}


  public void keyReleased(KeyEvent arg0) {}


  public void keyTyped(KeyEvent evt) {
    if(evt.getKeyChar() == 'o' && evt.isAltGraphDown()){
      setText(getText() + "ö");
      evt.consume();
    }
  }


}

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public void keyTyped(KeyEvent evt) {
    if(evt.getKeyChar() == 'ó'){
      setText(getText() + "ö");
      evt.consume();
    }
  }

package daswort.gui;

import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.HashMap;
import java.util.Map;

import javax.swing.JTextField;

public class GermanTextField extends JTextField implements KeyListener{

  private Map<Integer, String> transform =
      new HashMap<Integer, String>();

  public GermanTextField() {
    init();
  }


  public GermanTextField(int columns) {
    super(columns);
    init();
  }


  public GermanTextField(String text, int columns) {
    super(text, columns);
    init();
  }


  public GermanTextField(String text) {
    super(text);
    init();
  }


  private void init() {
    transform.put(KeyEvent.VK_A, "äÄ");
    transform.put(KeyEvent.VK_U, "üÜ");
    transform.put(KeyEvent.VK_O, "öÖ");

    addKeyListener(this);
  }



  public void keyPressed(KeyEvent evt) {
    if(evt.isAltGraphDown()){
      String umlaut = transform.get(evt.getKeyCode());
      if(umlaut != null){
        int idx = evt.isShiftDown() ? 1 : 0;
        setText(getText() + umlaut.charAt(idx));
      }
    }
  }

  public void keyReleased(KeyEvent arg0) {}


  public void keyTyped(KeyEvent evt) {
    if(evt.isAltGraphDown()){
      evt.consume();
    }
  }


}

if (evt.getKeyCode() == KeyEvent.VK_O && evt.isAltGraphDown())

Object fontDefinition = new UIDefaults.ProxyLazyValue("javax.swing.plaf.FontUIResource", null, new Obje

java.util.Enumeration keys = UIManager.getDefaults().keys();
while (keys.hasMoreElements()) {
    Object key = keys.nextElement();
    Object value = UIManager.get(key);
    if (value instanceof javax.swing.plaf.FontUIResource) {
        UIManager.put(key, fontDefinition);
    }
}