多個線程與管道流進行通信並使用PushbackInputStream

Question

問題如下：

創建3個主題。

• 第一個將產生10張隨機數，
• 第二將總結偶數的這些10.
• 第三將總結奇數相同的10支隨機數的。

我的問題是：在第二個線程我讀所有的數字和他們推回到流，但是當第三線程想要從流中讀取，讀取第一個值是-1？！

下面是代碼：

//main program 
import java.io.*; 
public class anonymous { 

public static void main(String[] args) throws IOException, InterruptedException { 
    final PipedOutputStream out= new PipedOutputStream(); 
    final PipedInputStream in= new PipedInputStream(out); 
    Thread1 th1 = new Thread1(out); 
    Thread2 th2 = new Thread2(in); 
    Thread3 th3 = new Thread3(in); 
    Thread t1 = new Thread(th1); 
    Thread t2 = new Thread(th2); 
    Thread t3 = new Thread(th3); 
    t1.start(); 
    t2.start(); 
    t2.join(); 
    t3.start(); 
    t3.join(); 
    System.out.println("main finished."); 
} 
} 

//Thread1 
import java.io.*; 
import java.util.Random; 
public class Thread1 implements Runnable{ 
PipedOutputStream out=null; 
Random r = new Random(); 
public Thread1(PipedOutputStream send){ 
    this.out = send; 
} 
public void run(){ 
    int num; 
    System.out.println("thread 1 generated random numbers: "); 
    try{ 
    for (int i=0; i<10; i++) 
     { 
     num=r.nextInt(10); 
     System.out.print(num + " "); 
     out.write(num); 
     } 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 
try { 
    out.close(); 
} catch (IOException e) { 
    e.printStackTrace(); 
} 
System.out.println("\nthread 1 finished"); 
} 
} 

//Thread2 
import java.io.*; 
public class Thread2 implements Runnable{ 
PipedInputStream in=null; 
public Thread2(PipedInputStream get){ 
    this.in = get; 

} 
public void run(){ 
    PushbackInputStream push = new PushbackInputStream(in , 10); 
    //PushbackInputStream takes an InputStream and it will read the first 10 bytes 
      // in the stream and push them back to the stream 
    try { 
     byte[] byteArr = new byte[10]; 
     int i, sum=0, idx=0; 
     i=push.read(); 
     while (i != -1) 
     { 
      if(i%2 == 0) 
       sum += i; 
      byteArr[idx]=(byte) i; 
      i=push.read(); 
      idx++; 
     } 
     push.unread(byteArr,0 , 10); 
     System.out.println("thread 2: the sum of even random numbers: " + sum); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 
System.out.println("thread 2 finished"); 
} 
} 

//Thread3 
import java.io.*; 
public class Thread3 implements Runnable{ 

PipedInputStream in; 
public Thread3(PipedInputStream get){ 
    this.in = get; 
} 
public void run(){ 
    try { 
     int i, sum=0; 
     i=in.read(); 
     while (i != -1) 
     { 
      if(i%2 == 1) 
       sum += i; 
      i=in.read(); 
     } 
     System.out.println("thread 3: the sum of odd random numbers: " + sum); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 
    try { 
     in.close(); 
    } catch (IOException e){ 
     e.printStackTrace(); 
    } 
System.out.println("thread 3 finished"); 
} 
} 

輸出如下：

線程1產生的隨機數：
線程1成品
線程2：偶數隨機數之和：26
線程2完成
t hread 3：奇數隨機數之和：0
線程3完成
主要完成。

Answer 1

您應該在第二個和第三個流之間使用另一個管道，而不是濫用後推功能。