1.使用synchronized关键字同步线程
package step2;

public class Task {

	public static void main(String[] args) {

		final insertData insert = new insertData();

		for (int i = 0; i < 3; i++) {
			new Thread(new Runnable() {
				public void run() {
					insert.insert(Thread.currentThread());
				}
			}).start();
		}

	}
}

class insertData {

	public static int num = 0;

	/********* Begin *********/
	public synchronized void insert(Thread thread) {

		for (int i = 0; i <= 5; i++) {
			num++;
			System.out.println(num);
		}
	}

	/********* End *********/
}