ok ho capito come sfrutta il tasto invio l'esempio.. non ho avuto tempo ancora di rimodificare la struttura secondo il tuo post precedente.. però ho fatto che nella classe che implementa il JFrame al campo JTextField associo il mio listener..

public class Finestra extends JFrame{
...
final MyListener listener = new MyListener();
private final JTextField campo;
...
campo.addActionListener(listener);
...



public class MyListener implements ActionListener{
...
public void actionPerformed(ActionEvent ev){
if (frame.campo.getText().length() > 0) {
String s=frame.getAreaTesto().getText();
System.out.println(s);
frame.campo.setText("");
frame.area.setText(frame.nome+"--->"+s+"\n"); //subito sotto il JTextField ho una JTextArea dove voglio
scrivere il contenuto inserito nel JTextField
frame.campo.requestFocusInWindow(); //che a breve mi andrò a cercare a cosa serve
...
}

purtroppo mi da errore non a tempo di compilazione ma di esecuzione:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at MyListener.actionPerformed(MyListener.java:19)
at javax.swing.JTextField.fireActionPerformed(JTextFi eld.java:509)
at javax.swing.JTextField.postActionEvent(JTextField. java:722)
at javax.swing.JTextField$NotifyAction.actionPerforme d(JTextField.java:837)
at javax.swing.SwingUtilities.notifyAction(SwingUtili ties.java:1664)
at javax.swing.JComponent.processKeyBinding(JComponen t.java:2851)
at javax.swing.JComponent.processKeyBindings(JCompone nt.java:2886)
at javax.swing.JComponent.processKeyEvent(JComponent. java:2814)
at java.awt.Component.processEvent(Component.java:598 0)
at java.awt.Container.processEvent(Container.java:210 5)
at java.awt.Component.dispatchEventImpl(Component.jav a:4564)
at java.awt.Container.dispatchEventImpl(Container.jav a:2163)
at java.awt.Component.dispatchEvent(Component.java:43 90)
at java.awt.KeyboardFocusManager.redispatchEvent(Keyb oardFocusManager.java:1881)
at java.awt.DefaultKeyboardFocusManager.dispatchKeyEv ent(DefaultKeyboardFocusManager.java:749)
at java.awt.DefaultKeyboardFocusManager.preDispatchKe yEvent(DefaultKeyboardFocusManager.java:1025)
at java.awt.DefaultKeyboardFocusManager.typeAheadAsse rtions(DefaultKeyboardFocusManager.java:892)
at java.awt.DefaultKeyboardFocusManager.dispatchEvent (DefaultKeyboardFocusManager.java:713)
at java.awt.Component.dispatchEventImpl(Component.jav a:4434)
at java.awt.Container.dispatchEventImpl(Container.jav a:2163)
at java.awt.Window.dispatchEventImpl(Window.java:2478 )
at java.awt.Component.dispatchEvent(Component.java:43 90)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.j ava:649)
at java.awt.EventQueue.access$000(EventQueue.java:96)
at java.awt.EventQueue$1.run(EventQueue.java:608)
at java.awt.EventQueue$1.run(EventQueue.java:606)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectio nPrivilege(AccessControlContext.java:105)
at java.security.AccessControlContext$1.doIntersectio nPrivilege(AccessControlContext.java:116)
at java.awt.EventQueue$2.run(EventQueue.java:622)
at java.awt.EventQueue$2.run(EventQueue.java:620)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectio nPrivilege(AccessControlContext.java:105)
at java.awt.EventQueue.dispatchEvent(EventQueue.java: 619)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(EventDispatchThread.java:275)
at java.awt.EventDispatchThread.pumpEventsForFilter(E ventDispatchThread.java:200)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(EventDispatchThread.java:190)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:185)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:177)
at java.awt.EventDispatchThread.run(EventDispatchThre ad.java:138)

te l'ho postato giusto per fartelo vedere se ti serve..