Design Patterns in Android development-a detailed explanation of the singleton pattern

Design Patterns in Android development-a detailed explanation of the singleton pattern:
1. Characteristics of the singleton mode:
(1). Ensure that there is only one instance of a class
(2). Provides a global access point that can be accessed to him.
(3). The constructor is declared private, thereby preventing the creation of objects outside the class
2. Type:
(1). A hungry man single-case mode
(2). Lazy single-case mode
3. Code Analysis:
(1). A hungry man single-case mode:

  //类加载的时候对象就实例化了。  privatestaticnew Single();    publicstaticgetInstance() {        return mSingle;    //缺点：不能保证有其他的方式导致类加载，这时候对象实例化没有达到延迟加载的效果      

(2). Lazy Singleton mode: (thread-safe), (second use this way)

publicstaticgetInstance2() {        synchronized (Single.class) {            ifnull) {                new Single();            }        }        return mSingle2;    }  //这个类只有一个实例，在多线程的时候也是创建一个实例。同一时间内只有一个线程调用这个方法，若有多个线程同时访问这个方法的话，其它的线程必须等待。//如果没有这个关键字，在多线程的时候就会创建两个或者多个实例.这种方式效率比较低。

(3). Internal class Mode: (Recommended Use this way)

privatestaticclass SingleHolder {       privatestaticnew Single();    }publicstaticgetInstance03() {     return//保证了对象初始化的时候只有一个线程。类加载的时候也没有主动初始化对象。只是在调用getInstance03()方法的时候加载了SingleHolder。达到了延迟加载的效果。

Design Patterns in Android development-a detailed explanation of the singleton pattern