单例设计模式

单例设计模式分为两种：

1. 在类被加载时初始化对象，称为SingletonPattern

• 在类被使用时初始化对象(延迟加载)，称为LazySingletonPattern

SingletonPattern

public class C09_SingletonPattern {
    private C09_SingletonPattern(){
        System.out.println("C09_SingletonPattern was created...");
    }
    //类被加载时创建实例
    private static C09_SingletonPattern instant = new C09_SingletonPattern();
    public static C09_SingletonPattern getInstant(){
        return instant;
    }
    //用于加速加载该类
    public static void load(){}
}

LazySingletonPattern

public class C10_LazySingletonPattern {
    private C10_LazySingletonPattern(){}
    private static class SingletonPatternHolder{
        private static C10_LazySingletonPattern instant = new C10_LazySingletonPattern();
    }
    public static C10_LazySingletonPattern getInstant(){
        return SingletonPatternHolder.instant;
    }
}