饿汉模式-初始化加载

public class HungryManSingleton {

private HungryManSingleton() {

}

// 使用private static修饰

private static HungryManSingleton hungryManSingleton = new HungryManSingleton();

public static HungryManSingleton getHungryManSingleton() {

return hungryManSingleton;

}

}

饿汉模式-延时加载(建议用这种)

public class HungryManSingleton {

private HungryManSingleton() {

}

// 内部静态类,懒加载

public static HungryManSingleton getInstance() {

return InnerStaticClass.hungryManSingleton;

}

static class InnerStaticClass {

private static HungryManSingleton hungryManSingleton = new HungryManSingleton();

}

}

懒汉模式

public class LazyManSingleton {

private LazyManSingleton() {

}

// volatile防止指令重排

private static volatile LazyManSingleton lazyManSingleton;

public static LazyManSingleton getLazyManSingleton() {

// 双重判断double check

if (lazyManSingleton == null) {

synchronized (LazyManSingleton.class) {

if (lazyManSingleton == null) {

lazyManSingleton = new LazyManSingleton();

}

}

}

return lazyManSingleton;

}

}