I have a ConcurrentMap and I put elements from an ArrayList to the map for other threads to process. Once a thread finishes its processing it adds the result in the ConcurrentMap and calls a method in order for let's say the "main" thread to get and process all the results (from both the ConcurrentMap and the ArrayList).
This approach works but has a result to call the method as many times as the number of elements in the list.
Question: What constructs can I use so that the method is called once, after the ConcurrentMap is fully populated by the results of all background threads?
我有一个ConcurrentMap，我将ArrayList中的元素放到地图上，供其他线程处理。一旦线程完成其处理，它就会在ConcurrentMap中添加结果并调用一个方法，让我们说“主”线程来获取并处理所有结果（来自ConcurrentMap和ArrayList）。这种方法有效，但结果是调用方法的次数与列表中的元素数一样多。问题：在ConcurrentMap完全填充所有后台线程的结果之后，我可以使用哪些构造来调用方法一次？
2 个解决方案
#1
1
You can use CountDownLatch initialize it with total items in Arraylist and every time a item in process count it down using countDown method,
您可以使用CountDownLatch将其初始化为Arraylist中的总项目，并且每当正在处理的项目使用countDown方法对其进行计数时，
Main thread can call await method on latch, await blocks the thread till counter reaches zero.
主线程可以在锁存器上调用await方法，等待阻塞线程直到计数器达到零。
#2
0
In Java 8 you can do this
在Java 8中，您可以执行此操作
ConcurrentMap<Key, Value> map = ...
listToProcess.parallelStream().forEach(e -> addElementToMap(e, map));
This will perform the processing of all the element using all the CPUs you have and only return when they are all done.
这将使用您拥有的所有CPU执行所有元素的处理，并且只有在完成后才返回。
#1
1
You can use CountDownLatch initialize it with total items in Arraylist and every time a item in process count it down using countDown method,
您可以使用CountDownLatch将其初始化为Arraylist中的总项目，并且每当正在处理的项目使用countDown方法对其进行计数时，
Main thread can call await method on latch, await blocks the thread till counter reaches zero.
主线程可以在锁存器上调用await方法，等待阻塞线程直到计数器达到零。
#2
0
In Java 8 you can do this
在Java 8中，您可以执行此操作
ConcurrentMap<Key, Value> map = ...
listToProcess.parallelStream().forEach(e -> addElementToMap(e, map));
This will perform the processing of all the element using all the CPUs you have and only return when they are all done.
这将使用您拥有的所有CPU执行所有元素的处理，并且只有在完成后才返回。