Using Collections.synchronizedMap
package com.logicbig.example.collections;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
public class SynchronizedMapExample2 {
private static AtomicInteger counter = new AtomicInteger();
public static void main(String... args) throws InterruptedException {
Map<Integer, Integer> m = new HashMap<>();
Map<Integer, Integer> map = Collections.synchronizedMap(m);
final ExecutorService e = Executors.newFixedThreadPool(10);
for (int i = 0; i < 10000; i++) {
e.execute(() -> map.put(counter.incrementAndGet(),
(int) (Math.random() * 100)));
}
e.shutdown();
e.awaitTermination(1000, TimeUnit.SECONDS);
System.out.println(map.size());//should be 10000
}
}
Output
10000