单例设计模式

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前言一、懒汉式二、饿汉式三.双重加锁

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新手上道，仅供学习和参考，有错误请见谅

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//懒汉式
public class Singleton1 {
    //私有构造
    private Singleton1() {
    }
    private static Singleton1 singleton1 = null;
    public static Singleton1 getInstance(){
        if (singleton1==null){
            singleton1 = new Singleton1();
        }
        return singleton1;
    }

}

//饿汉式
public class Singleton1 {
    //私有构造器
    private Singleton1() {
    }
    private static Singleton1 singleton1 = new Singleton1();
    public static Singleton1 getInstance(){
        return singleton1;
    }

}

//双重加锁
public class Singleton1{
    private Singleton1(){
    }
    private static Singleton1 singleton1 = null;
    public static Singleton1 getInstance(){
        if (singleton1 == null) {
            synchronized (Singleton1.class) {
                if (singleton1 == null) {
                    singleton1 = new Singleton1();
                }
            }
        }
        return singleton1;
      }
}