java多線程按順序輸出

4個線程,A線程輸出A,B線程輸出B,C線程輸出C,D線程輸出D  輸出格式爲:ABCDABCDABCDABCDABCDABCDABCDABCDABCD....

代碼如下:

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class ThreadTest extends Thread {
	private static String tmp;//輸出字符串
	private static Lock lock = new ReentrantLock();
	private static int state = 0;
	static boolean flag;

	public static String multiThreadWrite(final int times) {
		tmp = new String();
		flag = false;
		Thread threadA = new Thread() {
			public void run() {
				int count = 0;

				while (count < times) {
					lock.lock();
					if (state % 4 == 0) {

						tmp += "A";
						state++;
						count++;
					}
					lock.unlock();
				}

			}
		};

		Thread threadB = new Thread() {

			public void run() {
				int count = 0;

				while (count < times) {

					lock.lock();
					if (state % 4 == 1) {

						tmp += "B";
						state++;
						count++;
					}
					lock.unlock();
				}

			}
		};

		Thread threadC = new Thread() {
			public void run() {
				int count = 0;

				while (count < times) {
					lock.lock();
					if (state % 4 == 2) {
						tmp += "C";
						state++;
						count++;
					}
					lock.unlock();
				}

			}
		};

		Thread threadD = new Thread() {

			public void run() {
				int count = 0;

				while (count < times) {
					lock.lock();
					if (state % 4 == 3) {
						tmp += "D";
						state++;
						count++;
					}
					lock.unlock();
				}
				flag = true;
			}
		};

		threadA.start();
		threadB.start();
		threadC.start();
		threadD.start();
		while (!flag)
			; // 防止main線程在四個線程執行完之前就返回tmp值
		return tmp;
	}

	public static void main(String[] args) {
		String ss = multiThreadWrite(3);
		System.out.println(ss);
	}
}

輸出結果:ABCDABCDABCD