三个线程abc顺序执行
2024-08-28 03:05:14
1.使用synchronized悲观锁
（秋招阿里的一个笔试题，应该写的比较复杂，然后就没有然后了o(╥﹏╥)o）
public class ThreadThreadp {
private int flag = 0;
public synchronized void printa() throws InterruptedException {
while (true)
{
if(flag ==0)
{
System.out.print("A");
flag = 1;
notifyAll();
}
wait();
}
}
public synchronized void printb() throws InterruptedException {
while (true)
{
if(flag ==1)
{
System.out.print("B");
flag = 2;
notifyAll();
}
wait();
}
}
public synchronized void printc() throws InterruptedException {
while (true) {
if (flag == 2) {
System.out.print("C");
Thread.sleep(1000);
flag = 0;
notifyAll();
}
wait();
}
}
public static void main(String[]args) throws InterruptedException
{
ThreadThreadp t = new ThreadThreadp();
PrintA printA = new PrintA(t);
PrintB printB = new PrintB(t);
PrintC printC = new PrintC(t);
Thread t1 = new Thread(printA);
Thread t2 = new Thread(printB);
Thread t3 = new Thread(printC);
t1.start();
t2.start();
t3.start();
//Thread t11 = new Thread(printA);
//Thread t21 = new Thread(printB);
//Thread t31 = new Thread(printC);
//t11.start();
//t21.start();
//t31.start();
}
}
class PrintA implements Runnable{
private ThreadThreadp t;
PrintA(ThreadThreadp t){
this.t=t;
}
@Override
public void run() {
try {
t.printa();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
class PrintB implements Runnable{
private ThreadThreadp t;
PrintB(ThreadThreadp t){
this.t=t;
}
@Override
public void run() {
try {
t.printb();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
class PrintC implements Runnable{
private ThreadThreadp t;
PrintC(ThreadThreadp t){
this.t=t;
}
@Override
public void run() {
try {
t.printc();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
2.使用Lock+Condition
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock; public class threadsan {
public static void main(String [] args)
{
PrintABC printABC = new PrintABC();
new Thread(new Runnable() {
@Override
public void run() {
printABC.printA();
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
printABC.printB();
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
printABC.printC();
}
}).start();
}
} class PrintABC{
private final Lock lock = new ReentrantLock();
private Condition lockA = lock.newCondition();
private Condition lockB = lock.newCondition();
private Condition lockC = lock.newCondition();
int flag = 0; public void printA()
{
lock.lock();
try {
while (true)
{
while (flag!=0)
lockA.await();
System.out.print("A");
flag =1;
lockB.signal();
}
} catch (InterruptedException e) {
e.printStackTrace();
}finally {
lock.unlock();
}
}
public void printB()
{
lock.lock();
try {
while (true)
{
while (flag!=1)
lockB.await();
System.out.print("B");
flag =2;
lockC.signal();
}
} catch (InterruptedException e) {
e.printStackTrace();
}finally {
lock.unlock();
}
}
public void printC()
{
lock.lock();
try {
while (true)
{
while (flag!=2)
lockC.await();
System.out.print("C");
Thread.sleep(1000);
flag =0;
lockA.signal();
}
} catch (InterruptedException e) {
e.printStackTrace();
}finally {
lock.unlock();
}
}
}
3.使用Semaphore实现
//semaphore没用过。。。参考
import java.util.concurrent.Semaphore; /**
* Created by huali on 2018/7/25.
*/
public class PrintABCRotationUsingSemaphore {
public static void main(String[] args) {
PrintABCUsingSemaphore printABC = new PrintABCUsingSemaphore();
new Thread(() -> printABC.printA()).start();
new Thread(() -> printABC.printB()).start();
new Thread(() -> printABC.printC()).start();
}
} class PrintABCUsingSemaphore {
private Semaphore semaphoreA = new Semaphore(1);
private Semaphore semaphoreB = new Semaphore(0);
private Semaphore semaphoreC = new Semaphore(0);
//private int attempts = 0; public void printA() {
print("A", semaphoreA, semaphoreB);
} public void printB() {
print("B", semaphoreB, semaphoreC);
} public void printC() {
print("C", semaphoreC, semaphoreA);
} private void print(String name, Semaphore currentSemaphore, Semaphore nextSemaphore) {
for (int i = 0; i < 10; ) {
try {
currentSemaphore.acquire();
//System.out.println(Thread.currentThread().getName()+" try to print "+name+", attempts : "+(++attempts));
System.out.println(Thread.currentThread().getName() +" print "+ name);
i++;
nextSemaphore.release();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
另外参考链接 三个线程轮流执行顺序打印ABC（一）：使用Semaphore实现
使用信号量Semaphore循环打印ABC
三个线程轮流执行顺序打印ABC（二）：使用Lock+Condition实现
三个线程轮流执行顺序打印ABC（三）：使用Lock实现
————————————————
版权声明：本文为CSDN博主「Angel_Zhl」的原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/qq_33915826/article/details/81205938
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