在java中使用多线程在文件中写入值

Question

我可能会在这里问一个重复的问题。 但仍然无法解决我的问题。

我试着为下面的问题找到答案。

编写一个程序来创建2个主题。线程1将在每次输入输出文件后以1秒的延迟写入数字1到10。线程2将在每次输入到同一输出文件后以两秒的延迟写入数字1到10。

重量我做

import java.io.BufferedWriter; 
import java.io.File; 
import java.io.FileWriter; 
import java.io.IOException; 

class Thread1 extends Thread 
{ 
     public void run() 
     { 

       ThreadSample threadSample = new ThreadSample(); 
       try { 
        threadSample.printer(500); 
       } catch (IOException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 

     } 
} 
class Thread2 extends Thread 
{ 
     public void run() 
     { 
       ThreadSample threadSample = new ThreadSample(); 
       try { 
        threadSample.printer(1000); 
       } catch (IOException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 

       /*{ 
        try { 
          for(int i=0;i<10;i++){ 
            System.out.println(this.getName()+" "+i); 

            Thread.sleep(1000); 
          } 
        } 
        catch (InterruptedException e) { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
        } 
       }*/ 
     } 
} 

    public class ThreadSample extends Thread{ 

      public void printer(int j) throws IOException{ 

        FileWriter f = new FileWriter("C:\\Users\\Desktop\\sample.txt"); 
        //f.getAbsoluteFile(); 

        BufferedWriter br = new BufferedWriter(f); 

        synchronized(this){ 
         try { 
           FileWriter fw=new FileWriter("C:\\Users\\BK00354083\\Desktop\\sample.txt"); 



           for(int i=0;i<10;i++){ 
             System.out.println(this.getName()+" "+i); 
             br.write("values"+ i); 
             br.newLine(); 
             Thread.sleep(j); 
           } 
         } 
         catch (InterruptedException e) { 
           // TODO Auto-generated catch block 
           e.printStackTrace(); 
         }finally { 
           br.close(); 
         } 
        } 
      } 

      public static void main(String args[]){ 
        Thread1 t1=new Thread1(); 
        Thread2 t2=new Thread2(); 

        t1.start(); 
        t2.start(); 
      } 
    } 

但写一个线程值转换成文件。 所以我改变了我的代码像下面

import java.io.BufferedWriter; 
    import java.io.File; 
    import java.io.FileWriter; 
    import java.io.IOException; 

    class Thread1 extends Thread 
    { 
     public void run() 
     { 
      FileWriter f; 
      try { 
       f = new FileWriter("C:\\Users\\Desktop\\sample.txt"); 

       BufferedWriter br = new BufferedWriter(f);   
       synchronized(this){ 
        try {       
         for(int i=0;i<10;i++){ 
          System.out.println(this.getName()+" "+i); 
          br.write("values"+ i); 
          br.newLine(); 
          Thread.sleep(500); 
         } 
        } 
        catch (InterruptedException e) { 
         // TODO Auto-generated catch block 
         e.printStackTrace(); 
        }finally { 
         br.close(); 
        } 
       } 
      } catch (IOException e1) { 
       e1.printStackTrace(); 
      } 
     } 
    } 
    class Thread2 extends Thread 
    { 
     public void run() 
     { 
      FileWriter f; 
      try { 
       f = new FileWriter("C:\\Users\\Desktop\\sample.txt"); 

       BufferedWriter br = new BufferedWriter(f);   
       synchronized(this){ 
        try {       
         for(int i=0;i<10;i++){ 
          System.out.println(this.getName()+" "+i); 
          br.append("values"+ i); 
          br.newLine(); 
          Thread.sleep(500); 
         } 
        } 
        catch (InterruptedException e) { 
         e.printStackTrace(); 
        }finally { 
         br.close(); 
        } 
       } 
      } catch (IOException e1) { 
       e1.printStackTrace(); 
      } 
     } 
    } 

    public class ThreadSample extends Thread{ 
      public static void main(String args[]){ 
      Thread1 t1=new Thread1(); 
      Thread2 t2=new Thread2(); 
      t1.start(); 
      t2.start(); 
     } 
    } 

即使在使用时也只写了相同的线程2的值 任何帮助.. !!!

Answer 1

您的第二个线程不会将内容追加到由第一个线程写入的文件。相反，它会覆盖第一个线程写入的内容。

所以你只能从第二个线程获得输出。

从

FileWriter f = new FileWriter("C:\\Users\\Desktop\\sample.txt"); 

更改代码

到

FileWriter f = new FileWriter("C:\\Users\\Desktop\\sample.txt",true); 

参考Java文档page上FileWriter

public FileWriter(File file, 
        boolean append) 
      throws IOException 

给定一个File对象构造一个FileWriter对象。如果第二个参数为true，则字节将写入文件的末尾而不是开头。