• 方式一(不含参)

  class Single private constructor() {    init {//初始化    }    private object Holder {        val INSTANCE = Single()    }    companion object {        val instance: Single by lazy { Holder.INSTANCE }    }}复制代码

• 方式二（带参数）

  class Singleton private constructor(str: String) {    init {        println("Init")    }    companion object {        @Volatile        var instance: Singleton? = null        fun getInstance(a: String) {            if (instance == null) {                synchronized(Singleton::class)                {                    if (instance == null) {                        instance = Singleton(a)                    }                }                return instance!!            }        }    }}复制代码

测试实现

fun main(args: Array
    
     ) {    Single.instance    Singleton.getInstance("a")}复制代码