kotlin单例模式（3）

线程安全的懒汉式

Java

public class Singleton{
    private static Singleton instance;
    private Singleton(){ }
    public static synchronized Singleton getInstance(){
        if(instance == null){
            instance = new Singleton();
        }
        return instance;
    }
}

kotlin

class Singleton private constructor(){
    companion obejct{
        private var instance:Singleton? = null
        get(){
            if(field == null) field = Singleton()
            return field
        }
        @Synchronized
        fun get():Singleton = instance!!
    }
}