Java设计模式--单例模式

package com.design.singleton;

public class EagerSingleton {

    private static final EagerSingleton EAGER_SINGLETON = new EagerSingleton();

    private EagerSingleton(){}

    public static EagerSingleton getInstance(){
        return EAGER_SINGLETON;
    }
}

package com.design.singleton;

public class LazySingleton {

    private static LazySingleton lazySingleton = null;

    private LazySingleton(){}

    public synchronized static LazySingleton getInstance(){
        if (lazySingleton == null){
            return new LazySingleton();
        }
        return lazySingleton;
    }

}

package com.design.singleton;

public class InnerSingleton {

    private InnerSingleton(){}

    private static class Inner{
        private static InnerSingleton Instance = new InnerSingleton();
    }

    public static InnerSingleton getInstance(){
        return Inner.Instance;
    }
    
    public void doSomething(){
        // do something
    }
    
}