静态类的有关问题

import java.awt.BorderLayout;import java.awt.Container;import java.util.Hashtable;import javax.swing.Action;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.JScrollPane;import javax.swing.JTextArea;import javax.swing.JTextField;import javax.swing.text.DefaultEditorKit;public class CutPasteSample {  public static void main(String args[]) {    JFrame frame = new JFrame("Cut/Paste Example");    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);    Container content = frame.getContentPane();    JTextField textField = new JTextField();    JTextArea textArea = new JTextArea();    JScrollPane scrollPane = new JScrollPane(textArea);    content.add(textField, BorderLayout.NORTH);    content.add(scrollPane, BorderLayout.CENTER);    Action actions[] = textField.getActions();    Action cutAction = TextUtilities.findAction(actions,        DefaultEditorKit.cutAction);    Action copyAction = TextUtilities.findAction(actions,        DefaultEditorKit.copyAction);    Action pasteAction = TextUtilities.findAction(actions,        DefaultEditorKit.pasteAction);    JPanel panel = new JPanel();    content.add(panel, BorderLayout.SOUTH);    JButton cutButton = new JButton(cutAction);    cutButton.setText("Cut");    panel.add(cutButton);    JButton copyButton = new JButton(copyAction);    copyButton.setText("Copy");    panel.add(copyButton);    JButton pasteButton = new JButton(pasteAction);    pasteButton.setText("Paste");    panel.add(pasteButton);    frame.setSize(250, 250);    frame.setVisible(true);  }}class TextUtilities {  private TextUtilities() {  }  public static Action findAction(Action actions[], String key) {    Hashtable commands = new Hashtable();    for (int i = 0; i < actions.length; i++) {      Action action = actions[i];      commands.put(action.getValue(Action.NAME), action);    }    return (Action) commands.get(key);  }}