A System Clipboard is a part of Swing and AWT API  that implements a mechanism to transfer data using cut/copy/paste operations.
With the flowing source code first we set a text into System Clipboard and then register a listener for printing change of the System Clipboard content.

package saeedswing;

import java.awt.Toolkit;

import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.FlavorEvent;
import java.awt.datatransfer.FlavorListener;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.UnsupportedFlavorException;

import java.io.IOException;
import javax.swing.JFrame;
import javax.swing.WindowConstants;

* @author Saeed Zarinfam
public class NewMain {

public static void main(String[] args) {
String someText = "Saeed";
StringSelection ss = new StringSelection(someText);
Clipboard systemClipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
systemClipboard.setContents(ss, null);

systemClipboard.addFlavorListener(new FlavorListener() {

public void flavorsChanged(FlavorEvent e) {
try {
Clipboard clipboard = (Clipboard) e.getSource();
System.out.println("flavorsChanged : "

+ clipboard.getContents(null).getTransferData(DataFlavor.stringFlavor));
} catch (UnsupportedFlavorException ex) {
} catch (IOException ex) {

JFrame jFrame = new JFrame();

have a nice time.