Test Java Synchronization.

TestSynchronization.java

import java.lang.Thread;
import java.util.concurrent.atomic.AtomicInteger;

public class TestSynchronization {

	public static void main(String[] args) {
		Task task = new Task();
		for (int i = 0; i < 100; i++) {
			new Thread(task).start();
		}
		try {
			Thread.sleep(2000);
		} catch (Exception e) {
			e.printStackTrace();
		}
//		task.printNum();
		task.printNum2();
	}

}

class Task implements Runnable {
	private int num = 0;
	private AtomicInteger num2 = new AtomicInteger(0);
	
	public synchronized void inc() {
		num++;
	}

	public void inc2() {
		num2.getAndIncrement();
	}

	@Override
	public void run() {
		for (int i = 0; i < 10000; i++) {
//			inc();
			inc2();
		}
		System.out.println("finish");
	}

	public void printNum() {
		System.out.println("num : " + num);
	}

	public void printNum2() {
		System.out.println("num2 : " + num2);
	}
}