Java Thread How to - Use ConcurrentHashMap in Executors

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Question

We would like to know how to use ConcurrentHashMap in Executors.

Answer

import java.util.Map;
import java.util.Random;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
// www  .j a  v  a 2s  .  c  om
public class Main {
  public static int MAP_SIZE = 100000;
  public static void main(String[] args) {
    Map<String, String> map = new ConcurrentHashMap<String, String>();
    for (int i = 0; i < MAP_SIZE; i++) {
      map.put("key:" + i, UUID.randomUUID().toString());
    }
    ExecutorService executor = Executors.newCachedThreadPool();
    Accessor a1 = new Accessor(map);
    Accessor a2 = new Accessor(map);
    Mutator m = new Mutator(map);
    executor.execute(a1);
    executor.execute(m);
    executor.execute(a2);
  }
}

class Accessor implements Runnable {
  Map<String, String> map;
  public Accessor(Map<String, String> map) {
    this.map = map;
  }
  @Override
  public void run() {
    for (Map.Entry<String, String> entry : this.map.entrySet()) {
      System.out.println(Thread.currentThread().getName() + " - ["
          + entry.getKey() + ", " + entry.getValue() + ']');
    }
  }
}

class Mutator implements Runnable {
  Map<String, String> map;
  Random random = new Random();
  public Mutator(Map<String, String> map) {
    this.map = map;
  }
  @Override
  public void run() {
    for (int i = 0; i < 100; i++) {
      this.map.remove("key" + random.nextInt(Main.MAP_SIZE));
      this.map.put("key" + random.nextInt(Main.MAP_SIZE), UUID.randomUUID()
          .toString());
      System.out.println(Thread.currentThread().getName() + ": " + i);
    }
  }
}

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