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import java.util.*; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicInteger; public class CollectionsSynchronizedMapExample3 { 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 } }
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