GlobalScope.launch(Main) 中的同步函数：Kotlin

Question

Scenerio: let fun A() and fun B() be two functions. Inside A() we are calling B( ). B() execution time takes around 5sec and meanwhile some other thread call A() again, then I am getting ConcurrentModificationException .

fun A(){
  GlobalScope.launch(Main) {
    val result = withContext(IO) {
      B()
    }
    if (this@activity.isValid()) {
      suggestedFeedItems = result
    } else {

    }
  }
} 

fun B(){
   //some code that takes some time to execute
}

How to synchronise it so that at a time one thread can execute B(). I already tried to use @synchronise . As im new in kotlin, Please suggest.

Answer 1

Problem seems to be exist in fun B() , where you might be doing loop in some Collection type (sa List, Stack...) and also deleting/inserting new element to that Collection type.

If that is the case, you should use Iterator to loop and you can delete/insert items while iterating. But if one thread is looping and other thread is inserting/deleting items, you need to synchronize access to that Collection type (using @Synchronized fun B() etc...).