Java Collections - Collections.synchronizedSet() Examples

package com.logicbig.example.collections;

import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

public class SynchronizedSetExample {
    private static AtomicInteger atomicInteger = new AtomicInteger();

    public static void main(String... args) throws InterruptedException {
        Set<Integer> set = new HashSet<>();
        System.out.println("initial set size: " + set.size());

        final ExecutorService e = Executors.newFixedThreadPool(10);
        for (int i = 0; i < 1000; i++) {
            e.execute(() -> set.add(atomicInteger.incrementAndGet()));
        }
        e.shutdown();
        e.awaitTermination(1000, TimeUnit.SECONDS);
        System.out.println(set.size());//should be 1000
    }
}

package com.logicbig.example.collections;

import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

public class SynchronizedSetExample2 {
    private static AtomicInteger atomicInteger = new AtomicInteger();

    public static void main(String... args) throws InterruptedException {
        Set<Integer> s = new HashSet<>();
        Set<Integer> set = Collections.synchronizedSet(s);
        System.out.println("initial set size: " + set.size());

        final ExecutorService e = Executors.newFixedThreadPool(10);
        for (int i = 0; i < 1000; i++) {
            e.execute(() -> set.add(atomicInteger.incrementAndGet()));
        }
        e.shutdown();
        e.awaitTermination(1000, TimeUnit.SECONDS);
        System.out.println(set.size());//should be 1000
    }
}