scala_object

scala object 线程安全

这篇Scala thread-safety question回复

提到如下代码：

object Class {
val students = new mutable.List()
}

“object” initialization is thread safe. “mutable.List” is not thread
safe and needs to be synchronized.

然后我们自己定义一个object用于测试：

  object  TestObject {

    val prop1 = "sad"

    lazy  val prop2 = "testLazy"
    println("propinitialize")
    private val props: java.util.Map[String, Object] = new java.util.HashMap[String, Object]

    props.put("prop2",prop2)//访问prop2的时候会给prop2赋值

    def initialize() = {
      println("initialize")
    }

    def apply() ={

      println(props.get("prop2").toString)
      println("initializing")
    }
}

用以下代码测试：

object  TestObjectInitializer extends  App {

  val exce = Executors.newFixedThreadPool(6)

  for (i <- 0.to(100)){
    val runner = new Runnable {
      def run(): Unit = {

        TestObject()
      }}
    exce.submit(runner)
  }

  println("initialized")
}

打印如下代码：

propinitializeinitializedtestLazytestLazyinitializingtestLazytestLazyinitializingtestLazytestLazyinitializinginitializing
initialized
testLazy
testLazy
initializing
testLazy
testLazy
initializing
testLazy
testLazy
initializing
initializing

propinitialize只执行一次。

参考资料：
Scala Singleton Object with Multi-threading
How to make object (a mutable stack) thread-safe