public class Singleton_ {
  //设为私有方法，防止被外部类引用或实例
  private Singleton_(){
    System.out.println("懒汉单例模式");
  }
  private static Singleton_ single = null;
  //并对外只暴露getInstance()方法，这是获取唯一实例方法。
  public static Singleton_ getInstance(){
    if(single==null)
      single = new Singleton_();
    return single;
  }
}

//饿汉式单例类.在类初始化时，已经自行实例化 
public class Singleton1 {
  private Singleton1() {}
  private static final Singleton1 single = new Singleton1();
  //对外只暴露getInstance()方法，这是获取唯一实例方法。
  public static Singleton1 getInstance() {
    return single;
  }
}

import javax.swing.JFrame;

public class Singleton_ extends JFrame{
  private static Singleton_ single = null;
  //对外只暴露getInstance()方法，这是获取唯一实例方法。
  public static Singleton_ getInstance(){
    if(single==null)
      single = new Singleton_();
    return single;
  }
  public static void main(String args[]){
    Singleton_ singleton_ = new Singleton_();//实例化唯一窗口与
    singleton_.setTitle("单例模式窗口");
    singleton_.setVisible(true);
  }
  //设为私有方法，防止被外部类引用或实例
  private Singleton_(){
    setBounds(100, 100, 461, 286);
    setContentPane(Panel_01.getInstance(this));
  }
}

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Panel_01 extends JPanel{
  private JButton but_01;
  private JPanel jPanel;
  private Panel_01(final JFrame jFrame){
    setLayout(null);
    System.out.println("正常");
    but_01 = new JButton("界面1");
    //点击事件
    but_01.addActionListener(new ActionListener() {
      
      @Override
      public void actionPerformed(ActionEvent e) {
        if(e.getSource()==but_01){
          jFrame.setContentPane(Panel_02.getInstance(jFrame));
          jFrame.validate();//使面板生效，刷新
        }
      }
    });
    but_01.setBounds(120, 45, 71, 28);
    jPanel = new JPanel();
    jPanel.setLayout(null);
    jPanel.setBounds(0, 76, 450, 224);
    jPanel.add(but_01);
    add(jPanel);
  }
  private static Panel_01 panel_01 = null;
  public static Panel_01 getInstance(JFrame jFrame){
    panel_01 = new Panel_01(jFrame);
    return panel_01;
  }
}

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Panel_02 extends JPanel{
  private JLabel jLabel = null;
  private JButton but_02 = null;
  //私有方法
  private Panel_02(JFrame jFrame){
    jLabel = new JLabel("界面1");
    jLabel.setBounds(0, 0, 100, 100);
    but_02 = new JButton("返回");
    //点击事件
    but_02.addActionListener(new ActionListener() {
      
      @Override
      public void actionPerformed(ActionEvent e) {
        if(e.getSource()==but_02){
          jFrame.setContentPane(Panel_01.getInstance(jFrame));
          jFrame.validate();//刷新
        }
      }
    });
    jLabel.setBounds(100, 100, 100, 100);
    add(but_02);
    add(jLabel);
  }
  private static Panel_02 panel_02=null;
  //对外接口
  public static Panel_02 getInstance(JFrame jFrame){
    panel_02 = new Panel_02(jFrame);
    return panel_02;
  }
}