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  • Java设计模式七种写法


    懒汉模式-线程不安全

    
    public class Singleton {
        private static Singleton instance;
        private Singleton (){
    
        }
    
        public static Singleton getInstance() {
            if (instance == null) {
                instance = new Singleton();
            }
            return instance;
        }
    }
    
    


    懒汉模式-线程安全

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


    饿汉模式

    
    public class Singleton {
        private static Singleton instance = new Singleton();
    
        private Singleton (){
    
        }
        
        public static Singleton getInstance() {
        	return instance;
        }
    }
    
    


    饿汉模式-变种

    
    public class Singleton {
        private static Singleton instance = null;
    
        static {
            instance = new Singleton();
        }
    
        private Singleton() {
    
        }
    
        public static Singleton getInstance() {
            return instance;
        }
    }
    
    


    静态内部类

    
    public class Singleton {
        private static class SingletonHolder {
    	    private static final Singleton INSTANCE = new Singleton();
        }
    
        private Singleton (){
    
        }
    
        public static final Singleton getInstance() {
    	    return SingletonHolder.INSTANCE;
        }
    }
    
    


    双重校验锁

    
    public class Singleton {
        private volatile static Singleton singleton;
        private Singleton (){
    
        }
        public static Singleton getSingleton() {
            if (singleton == null) {
                synchronized (Singleton.class) {
                    if (singleton == null) {
                        singleton = new Singleton();
                    }
                }
            }
            return singleton;
        }
    }
    
    


    枚举

    
    public enum Singleton {  
        INSTANCE;  
        public void whateverMethod() {  
        }  
    }  
    
    
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  • 原文地址:https://www.cnblogs.com/datiangou/p/10213622.html
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