Install your own action to text component : InputMap « Swing Event « Java Tutorial

1. Java Tutorial
2. Swing Event
3. InputMap

import java.awt.event.ActionEvent;

import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.KeyStroke;
import javax.swing.text.BadLocationException;
import javax.swing.text.JTextComponent;

class InsertAction extends AbstractAction {
  public InsertAction() {
    super("Insert Space");
  }

  public void actionPerformed(ActionEvent evt) {
    JTextComponent c = (JTextComponent) evt.getSource();

    try {
      c.getDocument().insertString(c.getCaretPosition(), " space", null);
    } catch (BadLocationException e) {
    }
  }
}

public class Main {
  public static void main(String[] argv) {
    JTextField component = new JTextField(10);
    InsertAction insertSpaceAction = new InsertAction();
    component.getInputMap(JComponent.WHEN_FOCUSED).put(
        KeyStroke.getKeyStroke(new Character(' '), 0), "none");

    component.getInputMap(JComponent.WHEN_FOCUSED).put(KeyStroke.getKeyStroke("pressed SPACE"),
        insertSpaceAction.getValue(Action.NAME));

    component.getActionMap().put(insertSpaceAction.getValue(Action.NAME), insertSpaceAction);

    JFrame f = new JFrame();
    f.add(component);
    f.setSize(300, 300);
    f.setVisible(true);
  }
}