单例模式

最新推荐文章于 2025-01-06 18:04:26 发布

ninety_two

最新推荐文章于 2025-01-06 18:04:26 发布

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分类专栏：设计模式

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本文深入探讨了单例模式的三种实现方式：懒汉模式、双检模式和静态内部类模式。通过代码示例，详细解释了每种模式的工作原理，并讨论了如何使用反射来破坏单例模式。

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1.懒汉模式

package 单例模式;

public class SingleTest {
	private static SingleTest instance;
	private SingleTest(){};
	public static synchronized SingleTest getStance(){
		if(instance==null){
			return new SingleTest();
		}
		return instance;
	}
}

2.双检模式

package 单例模式;

public class SingleTest {
	private static SingleTest instance;
	private SingleTest(){};
	public static  SingleTest getStance(){
		if(instance==null){
			synchronized(SingleTest.class){
				if(instance==null){
					return new SingleTest();
				}
				
			}
		}
		
		return instance;
	}
}

package 单例模式;

public class SingleTest {
	private SingleTest(){}
	public static SingleTest getStance(){
		return InstanceHolder.instance;
	}
	private static class InstanceHolder{
		private static SingleTest instance = new SingleTest();
	}
}

反射破解

package 单例模式;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

public class Test1 {

	public static void main(String[] args) throws NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		SingleTest instance = SingleTest.getStance();
		Constructor constructor = SingleTest.class.getConstructor();
		constructor.setAccessible(true);
		SingleTest instance2 = (SingleTest) constructor.newInstance();
		System.out.println(instance);
		System.out.println(instance2);
	}

}