多线程问题

张然龙

本帖最后由小白马__^o^ 于 2014-8-8 16:00 编辑

各位大神啊！帮小弟看一下这道程序，执行不下去啊！
程序要求是这样的：
有四个线程1、2、3、4。线程1的功能就是输出1，线程2的功能就是输出2，以此类推.........现在有四个文件ABCD。初始都为空。现要让四个文件呈如下格式：
A：1 2 3 4 1 2....
B：2 3 4 1 2 3....
C：3 4 1 2 3 4....
D：4 1 2 3 4 1....

这是小弟写的代码，可是就是有问题！还请大神们指导指导！

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.*;
public class Test06
{
public static void main(String args[])
{
ShiXian shi = new ShiXian();
ExecutorService service = Executors.newFixedThreadPool(4); //实例化一个线程池，池里面可以放4个线程
service.execute(new Thread(new Thread01(shi))); //将线程1放进去池中进行执行
service.execute(new Thread(new Thread02(shi)));
service.execute(new Thread(new Thread03(shi)));
service.execute(new Thread(new Thread04(shi)));
}
}
class ShiXian
{
Lock lock = new ReentrantLock();
Condition ThreadA = lock.newCondition();
Condition ThreadB = lock.newCondition();
Condition ThreadC = lock.newCondition();
Condition ThreadD = lock.newCondition();
int flag = 1;
//int [] buff = new int[6];
public void lock01() //加锁方法1
{
for (int i=1; i <=6;)
{
lock.lock();
try
{
while(flag != 1)
{
try
{
ThreadA.await();
}
catch (Exception e)
{
e.printStackTrace();
}
}
System.out.print(1 + " ");
//buff[0] = flag;
flag = 2;
ThreadB.signal();
i++ ;
}
finally
{
lock.unlock();
}
}
}
public void lock02() //加锁方法2
{
for (int i=1; i <=6; i++ )
{
lock.lock();
try
{
while(flag != 2)
{
try
{
ThreadA.await();
}
catch (Exception e)
{
e.printStackTrace();
}
}
System.out.print(2 + " ");
//System.out.println();
//buff[1] = flag;
flag = 3;
ThreadC.signal();
i++ ;
}
finally
{
lock.unlock();
}
}
}
public void lock03() //加锁方法3
{
for (int i=1; i <=6; i++ )
{
lock.lock();
try
{
while(flag != 3)
{
try
{
ThreadA.await();
}
catch (Exception e)
{
e.printStackTrace();
}
}
System.out.print(3 + " ");
//buff[2] = flag;
flag = 4;
ThreadD.signal();
i++ ;
}
finally
{
lock.unlock();
}
}
}
public void lock04() //加锁方法4
{
for (int i=1; i <=6; i++ )
{
lock.lock();
try
{
while(flag != 4)
{
try
{
ThreadA.await();
}
catch (Exception e)
{
e.printStackTrace();
}
}
System.out.print(4 + " ");
//buff[3] = flag;
flag = 1;
ThreadA.signal();
i++ ;
}
finally
{
lock.unlock();
}
}
}
}
class Thread01 implements Runnable //线程1
{
ShiXian shi = null;
public Thread01(ShiXian shi)
{
this.shi = shi;
}
public void run()
{
shi.lock01();
}
}
class Thread02 implements Runnable //线程2
{
ShiXian shi = null;
public Thread02(ShiXian shi)
{
this.shi = shi;
}
public void run()
{
shi.lock02();
}
}
class Thread03 implements Runnable //线程3
{
ShiXian shi = null;
public Thread03(ShiXian shi)
{
this.shi = shi;
}
public void run()
{
shi.lock03();
}
}
class Thread04 implements Runnable //线程4
{
ShiXian shi = null;
public Thread04(ShiXian shi)
{
this.shi = shi;
}
public void run()
{
shi.lock04();
}
}

复制代码

然后程序停在哪儿就不往下执行了，这是怎么回事儿啊！

天黑偷牛 · 天黑偷牛

额(⊙o⊙)…，我水平有点低，还没看懂

天黑偷牛 · 天黑偷牛

应该是死锁吧，我还没找到在哪

小白马__^o^ · 小白马__^o^

天黑偷牛发表于 2014-8-8 16:48
应该是死锁吧，我还没找到在哪

恩恩！我想应该也是死锁吧！但是就不知道怎么解决！哎！郁闷啊！还请大神指教！{:2_32:}

回头浪子心 · 回头浪子心

呵呵，，，我不会告诉你，我也不懂~~~

乐此不疲 · 乐此不疲

你的await跟sigal用的挺混乱的，应该交替A-B B-C C-D D-A这样保证循环，还有你的for循环中i++有时出现在for之后，有的出现在语句体中。。。帮你改了下

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.*;
public class Test06
{
public static void main(String args[])
{
ShiXian shi = new ShiXian();
ExecutorService service = Executors.newFixedThreadPool(4); //实例化一个线程池，池里面可以放4个线程
service.execute(new Thread(new Thread01(shi))); //将线程1放进去池中进行执行
service.execute(new Thread(new Thread02(shi)));
service.execute(new Thread(new Thread03(shi)));
service.execute(new Thread(new Thread04(shi)));
}
}
class ShiXian
{
Lock lock = new ReentrantLock();
Condition ThreadA = lock.newCondition();
Condition ThreadB = lock.newCondition();
Condition ThreadC = lock.newCondition();
Condition ThreadD = lock.newCondition();
int flag = 1;
//int [] buff = new int[6];
public void lock01() //加锁方法1
{
for (int i=1; i <=6;)
{
lock.lock();
try
{
while(flag != 1)
{
try
{
ThreadA.await();
}
catch (Exception e)
{
e.printStackTrace();
}
}
System.out.print(1 + " ");
//buff[0] = flag;
flag = 2;
ThreadB.signal();
i++ ;
}
finally
{
lock.unlock();
}
}
}
public void lock02() //加锁方法2
{
for (int i=1; i <=6; i++ )
{
lock.lock();
try
{
while(flag != 2)
{
try
{
ThreadA.await();
}
catch (Exception e)
{
e.printStackTrace();
}
}
System.out.print(2 + " ");
//System.out.println();
//buff[1] = flag;
flag = 3;
ThreadC.signal();
i++ ;
}
finally
{
lock.unlock();
}
}
}
public void lock03() //加锁方法3
{
for (int i=1; i <=6; i++ )
{
lock.lock();
try
{
while(flag != 3)
{
try
{
ThreadA.await();
}
catch (Exception e)
{
e.printStackTrace();
}
}
System.out.print(3 + " ");
//buff[2] = flag;
flag = 4;
ThreadD.signal();
i++ ;
}
finally
{
lock.unlock();
}
}
}
public void lock04() //加锁方法4
{
for (int i=1; i <=6; i++ )
{
lock.lock();
try
{
while(flag != 4)
{
try
{
ThreadA.await();
}
catch (Exception e)
{
e.printStackTrace();
}
}
System.out.print(4 + " ");
//buff[3] = flag;
flag = 1;
ThreadA.signal();
i++ ;
}
finally
{
lock.unlock();
}
}
}
}
class Thread01 implements Runnable //线程1
{
ShiXian shi = null;
public Thread01(ShiXian shi)
{
this.shi = shi;
}
public void run()
{
shi.lock01();
}
}
class Thread02 implements Runnable //线程2
{
ShiXian shi = null;
public Thread02(ShiXian shi)
{
this.shi = shi;
}
public void run()
{
shi.lock02();
}
}
class Thread03 implements Runnable //线程3
{
ShiXian shi = null;
public Thread03(ShiXian shi)
{
this.shi = shi;
}
public void run()
{
shi.lock03();
}
}
class Thread04 implements Runnable //线程4
{
ShiXian shi = null;
public Thread04(ShiXian shi)
{
this.shi = shi;
}
public void run()
{
shi.lock04();
}
}

复制代码

fantacyleo · fantacyleo

那么多锁，唯恐不死锁的节奏啊。。。其实用CyclicBarrier就很容易解决了。

import java.util.concurrent.*;
import java.io.*;
/** 有四个线程1、2、3、4。线程1的功能就是输出1，线程2的功能就是输出2，以此类推....现在有四个文件ABCD。初始都为空。现要让四个文件呈如下格式：
* A：1 2 3 4 1 2....
* B：2 3 4 1 2 3....
* C：3 4 1 2 3 4....
* D：4 1 2 3 4 1....
*
* 思路：
* 四个线程分别写四个文件，写好之后，在同一个CyclicBarrier上等待，执行barrier action，互换各自要写入的文件，再开始下一轮写入
*/
public class MultipleThreadWriter {
public static void main(String[] args) throws Exception {
FileWriter file1 = new FileWriter("c:\\1.txt");
FileWriter file2 = new FileWriter("c:\\2.txt");
FileWriter file3 = new FileWriter("c:\\3.txt");
FileWriter file4 = new FileWriter("c:\\4.txt");
final ThreadWriter tw1 = new ThreadWriter(file1, '1');
final ThreadWriter tw2 = new ThreadWriter(file2, '2');
final ThreadWriter tw3 = new ThreadWriter(file3, '3');
final ThreadWriter tw4 = new ThreadWriter(file4, '4');
CyclicBarrier barrier = new CyclicBarrier(4, new Runnable() {
public void run() {
FileWriter temp1 = tw1.getFileWriter();
FileWriter temp2 = tw2.getFileWriter();
FileWriter temp3 = tw3.getFileWriter();
FileWriter temp4 = tw4.getFileWriter();
// 互换四个线程的写入文件
tw1.setFileWriter(temp4);
tw2.setFileWriter(temp1);
tw3.setFileWriter(temp2);
tw4.setFileWriter(temp3);
}
});
tw1.setBarrier(barrier);
tw2.setBarrier(barrier);
tw3.setBarrier(barrier);
tw4.setBarrier(barrier);
ExecutorService exec = Executors.newCachedThreadPool();
exec.execute(tw1);
exec.execute(tw2);
exec.execute(tw3);
exec.execute(tw4);
TimeUnit.MILLISECONDS.sleep(10);
exec.shutdownNow();
}
}
class ThreadWriter implements Runnable {
private FileWriter fw;
private char c;
private CyclicBarrier barrier;
public ThreadWriter(FileWriter fw, char c) {
this.fw = fw;
this.c = c;
}
public void setFileWriter(FileWriter fw) {
this.fw = fw;
}
public FileWriter getFileWriter() {
return fw;
}
public void setBarrier(CyclicBarrier barrier) {
this.barrier = barrier;
}
public void run() {
try {
while (!Thread.interrupted()) {
fw.write(c + " ");
barrier.await();
}
} catch(InterruptedException e) {
} catch(BrokenBarrierException e) {
} catch(IOException e) {
} finally {
try {
fw.close();
} catch (IOException e) {
}
}
}
}

复制代码

lcycr · lcycr

二楼的代码太给力了

小白马__^o^ · 小白马__^o^

fantacyleo 发表于 2014-8-8 21:03
那么多锁，唯恐不死锁的节奏啊。。。其实用CyclicBarrier就很容易解决了。

fantacyleo 大神啊！你真的太给力了！厉害！小弟受教了！{:2_32:}

刘小记. · 刘小记.

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