Android开发手写一个单例范例

双重判断的懒汉式

public class SingleTon {
    //需要注意的是volatile
    private static volatile SingleTon mInstance;

    private SingleTon() {

    }

    public static SingleTon getInstance() {
        if (mInstance == null) { 
            synchronized (SingleTon.class) {
                if (mInstance == null) {
                    mInstance=new SingleTon();
                }
            }
        }

        return mInstance;
    }
}

静态内部类实现的单例

public class SingletonWithInnerClass {

    private SingletonWithInnerClass(){

    }

    private static class SingletonHolder{
        private static SingletonWithInnerClass INSTANCE = new SingletonWithInnerClass();
    }

    public static SingletonWithInnerClass getInstance(){
        return SingletonHolder.INSTANCE;
    }

}