Question

我必须加载文件并在其中打印数据，但是线程都是并行运行的，因此几秒钟之后只显示最后一个文件中的数据。总共有七个文件，我将它们循环加载。

这是我的代码：

 public class thread extends Thread {

     private static final String String = null;
     static String file="Lab5File";
     static String output="test2.dat";
     static ArrayList<Thread> threadList = new ArrayList<Thread>();


 public static void main(String[] args) throws FileNotFoundException, UnsupportedEncodingException {

  threadList = new ArrayList<>();

     for (int l=1;l<8;l++ )  
     {

        thread1111 x = new thread1111(file+l+".dat");
        threadList.add(x);
        x.start();
     }

     try {
         int ch = System.in.read();

     } catch (IOException e) {
       // TODO Auto-generated catch block
        e.printStackTrace();
     }

 } 


 public static class thread1111 extends Thread {
    String name ; 

    static DataOutputStream dos ;
    static FileOutputStream fos;
    static ArrayList<Thread> threadList;


    public thread1111(String fileName)
    {
        name = fileName;

          try {
            fos = new FileOutputStream("test2.dat");

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        dos = new DataOutputStream(fos);

    }

    public void run(){  

         InputStream is = null;
         DataInputStream dis = null;

         System.out.println("TRYING.........");

         try{

            // create input stream from file input stream
            is = new FileInputStream(name);

            // create data input stream
            dis = new DataInputStream(is);

        while (true) synchronized(dos)  {

                int Zip = dis.readInt();
                String City = dis.readUTF();
                String State = dis.readUTF();
                double Longitude =dis.readDouble();
                double Latitudes=dis.readDouble();
                int Zone = dis.readInt();
                int dst = dis.readInt();

                dos.writeInt(Zip);
                dos.writeUTF(City);
                dos.writeUTF(State);
                dos.writeDouble(Longitude);
                dos.writeDouble(Latitudes);
                dos.writeInt(Zone);
                dos.writeInt(dst);

               System.out.println(Zip+"\t"+City+"\t"+State+"\t"+Longitude+"\t"+Latitudes+"\t"+Zone+"\t"+dst+"\n");

            }

         }catch(Exception e){
                // if any I/O error occurs
                e.printStackTrace();
             }finally{

                // releases any associated system files with this stream
                if(is!=null)
                    try {
                        is.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                if(dis!=null)
                    try {
                        dis.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
             }   
   } 

 }}

Answer 1

几个选项，

您可以使用Thread.join
您可以使用CyclicBarrier来同步您的主题。
Single thread executor有足够大的队列（7）以满足您的需求。

Answer 2

只需使用Thread类，您需要调用join（）以同步线程：

Thread1.start();
Thread1.join();
Thread2.start();
Thread2.join();
Thread3.start();
Thread3.join();
...

您可以将主循环更改为

for (int l=1;l<8;l++ )  
   {
    thread1111 x = new thread1111(file+l+".dat");
    // threadList.add(x);
    x.start();
    x.join()
    }

然后循环将不会迭代到下一个线程，直到当前线程完成 - 当然你可以把整个循环放到它自己的线程中

Answer 3

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.ReentrantLock;

public class Test {

    public static void main(String[] args) {

        ExecutorService service = Executors.newFixedThreadPool(7);
        ReentrantLock lock = new ReentrantLock(true);
        for (int i = 0; i < 7; i++) {
            service.execute(new Runner("File" + i, lock));
        }
        service.shutdown();
    }

}

class Runner implements Runnable {
    String fileName;
    ReentrantLock lock;

    public Runner(String name, ReentrantLock lock) {
        this.fileName = name;
        this.lock = lock;
    }

    @Override
    public void run() {
        lock.lock();
        System.out.println("Current Thread: "
                + Thread.currentThread().getName() + " Executing file: "
                + fileName);
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        lock.unlock();
    }

}

将您的代码放在Runnable类的run方法中，以打印文件数据并根据您自己的需要进行更改。

同步线程，以便在Java中连续加载文件

3 个答案: