Clipboard cb = Toolkit.getDefaultToolkit().getSystemClipboard();

Transferable getContents(Object requester);
Void setContents(Transferable contents, ClipboardOwner owner);

Transferable tr = cb.getContents(this);
String s = (String) tr.getTransferData(DataFlavor.stringFlavor);

StringSelection ss = new StringSelection(this.jTextArea1.getText());
cb.setContents(ss,ss);

public class MainFrame extends JFrame {
private JPanel contentPane;
private BorderLayout borderLayout1 = new BorderLayout();
//创建新的组件
private JTextArea jTextArea1 = new JTextArea();
private JPanel jPanel1 = new JPanel();
private JButton jButton1 = new JButton();
private JButton jButton2 = new JButton();
//剪贴板实例
Clipboard cb = Toolkit.getDefaultToolkit().getSystemClipboard();
……
}

private void jbInit() throws Exception {
//setIconImage(Toolkit.getDefaultToolkit().createImage(MainFrame.class.getResource("[Your Icon]")));
contentPane = (JPanel) this.getContentPane();
contentPane.setLayout(borderLayout1);
this.setSize(new Dimension(396, 203));
this.setTitle("JClipboardDemo");
jButton1.setFont(new java.awt.Font("Dialog", 0, 14));
jButton1.setText("Copy");
jButton1.addActionListener(new java.awt.event.ActionListener() { //添加事件监听器
public void actionPerformed(ActionEvent e) {
jButton1_actionPerformed(e);
}
});
jButton2.setFont(new java.awt.Font("Dialog", 0, 14));
jButton2.setText("Paste");
jButton2.addActionListener(new java.awt.event.ActionListener() {//添加事件监听器
public void actionPerformed(ActionEvent e) {
jButton2_actionPerformed(e);
}
});
contentPane.add(jTextArea1, BorderLayout.CENTER);
contentPane.add(jPanel1, BorderLayout.SOUTH);
jPanel1.add(jButton1, null);
jPanel1.add(jButton2, null);
}

void jButton1_actionPerformed(ActionEvent e) {
StringSelection ss = new StringSelection(this.jTextArea1.getText()); //发送选中文本到系统剪贴板
cb.setContents(ss,ss);
}

void jButton2_actionPerformed(ActionEvent e) {
try{
Transferable tr = cb.getContents(this); //从系统剪贴板得到一个Transferable 对象
if (tr != null){
String s = (String) tr.getTransferData(DataFlavor.stringFlavor); //从Transferable 对象中得到文本数据
if (s!=null)
this.jTextArea1.insert(s,this.jTextArea1.getCaretPosition()); //在JTextArea 组件中的光标所在处插入文本
}
}catch(Exception err){
err.printStackTrace();
}
}