Kotlin实现单例模式

• 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 }
      }
  }

• 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!!
              }
          }
      }
  }

测试实现
      

fun main(args: Array<String>) {
    Single.instance

    Singleton.getInstance("a")
}