Java只打开一个窗口（窗口的单例模式）

版权声明：本文为博主原创文章，转载请声明出处并添加原文链接。 https://blog.csdn.net/qq_40299166/article/details/84851720

防止重复创建窗口，可以使用单例模式。

我写了个简单的例子来测试。点击两个不同的按钮，分别打开一个单例模式的窗口。

package com.singleton;

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

import javax.swing.*;


public class TestSingleton {
	private JFrame frame = new JFrame("测试");
	private JPanel p = new JPanel();
	private JButton btn1 = new JButton("弹出第一个窗口");
	private JButton btn2 = new JButton("弹出第二个窗口");
	
	private JFrame f1;
	private JFrame f2;
	
	public TestSingleton(){
		init();
	}
	
	public void init(){
		p.add(btn1);
		p.add(btn2);
		
		frame.add(p);
		frame.setSize(222, 222);
		frame.setLocation(50, 50);
		frame.setVisible(true);
		
		/*
		 * 给按钮添加事件监听器
		 */
		btn1.addActionListener(new ActionListener() {
			@Override
			public void actionPerformed(ActionEvent e) {
				f1 = Singleton1.getInstance();
				
				f1.setTitle("第一个窗口");
				f1.setSize(250, 180);
				f1.setLocation(270, 50);
				f1.setVisible(true);
			}
		});
		
		btn2.addActionListener(new ActionListener() {
			@Override
			public void actionPerformed(ActionEvent e) {
				f2 = Singleton2.getInstance();
				
				f2.setTitle("第二个窗口");
				f2.setSize(250, 250);
				f2.setLocation(270, 240);
				f2.setVisible(true);
			}
		});
	}
	
	/**
	 * 静态内部类实现单例模式
	 */
	public static class Singleton1 extends JFrame{
		/**
		 * 在静态内部类中定义单例对象
		 */
		public static class SingletonClass1{
			private static final Singleton1 instance = new Singleton1();
		}
		
		private Singleton1(){
			
		}
		
		public static Singleton1 getInstance(){
			return SingletonClass1.instance;
		}
	}
	
	public static class Singleton2 extends JFrame{
		public static class SingletonClass2{
			private static final Singleton2 instance = new Singleton2();
		}
		
		private Singleton2(){
			
		}
		
		public static Singleton2 getInstance(){
			return SingletonClass2.instance;
		}
	}
	
	public static void main(String[] args) {
		TestSingleton test = new TestSingleton();
	}
}