单例设计模式-枚举单例

public enum EnumSingleton {
    INSTANCE;
}

public class Test {
    public static void main(String[] args) {
        EnumSingleton instance1 = EnumSingleton.INSTANCE;
        EnumSingleton instance2 = EnumSingleton.INSTANCE;
        System.out.println(instance1 == instance2); // true
    }
}