用java写一个线程安全的单例饿汉模式

public class Singleton {
private static final Singleton INSTANCE = new Singleton();

private Singleton() {
}

public static Singleton getInstance() {
return INSTANCE;
}
}

// 使用 synchronized 关键字实现线程安全的单例饿汉模式
public class Singleton {
private static Singleton INSTANCE;

private Singleton() {
}

public static synchronized Singleton getInstance() {
if (INSTANCE == null) {
INSTANCE = new Singleton();
}
return INSTANCE;
}
}