java个人笔记之 i++ 线程不安全

public class Test {

	static int i = 0;
	
	public static void main(String[] args) {
		test1();
		//test2();
	}
	
	/**
	 * 不加锁
	 */
	public static void test1() {
		for (int j = 0; j < 100; j++)
			new Thread(() -> {try {
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			System.out.println(i++);}).start();
	}

	/**
	 * 加锁
	 */
	public static void test2() {
		for (int j = 0; j < 100; j++)
			new Thread(() -> {try {
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			synchronized (Test.class) {System.out.println(i++);}}).start();
	}
	
}