java - 如何将多线程写入单个文本文件？

Question

我想在一个文本文件上写两个线程，但它只出现了 PrintNum 部分而 PrintChar 不在文本文件中？如何将两个线程写入一个文件？有什么方法可以将两个线程组合成一个类，以便它可以输出到一个文件中吗？

这是我的代码:

import java.io.FileNotFoundException;
import java.io.PrintWriter;

public class Multithread {

    public static void main(String[] args) {    
        Runnable printA = new PrintChar('a', 500);
        Runnable print100 = new PrintNum(500);

        Thread thread1 = new Thread(printA);
        Thread thread2 = new Thread(print100);

        thread1.start();
        thread2.start();
    }
}

class PrintChar implements Runnable {
    private char charToPrint; 
    private int times;

    public PrintChar(char c, int t) {
        charToPrint = c;
        times = t;
    }

    @Override 
    public void run() {
        String fileName = "out.txt";
        try {
            PrintWriter outputStream = new PrintWriter(fileName);
            for (int i = 0; i < times; i++) {
                outputStream.print(charToPrint);
            }
            outputStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

class PrintNum implements Runnable {
    private int lastNum;

    public PrintNum(int n) {
        lastNum = n;
    }

    @Override 
    public void run() {
        String fileName = "out.txt";
        try {
            PrintWriter outputStream = new PrintWriter(fileName);
            for (int i = 1; i <= lastNum; i++) {
                outputStream.print(" " + i);
            }
            outputStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

Answer 1

试试这个。在这里，我在打印编写器中使用附加到文件。我没有对您的代码做太多更改。

import java.io.*;

public class Multithread {

  public static void main(String[] args) throws FileNotFoundException {
    String fileName = "out.txt";
    new PrintWriter(fileName).close();//to clear the text of the file
    Runnable printA = new PrintChar('a', 500);
    Runnable print100 = new PrintNum(500);

    Thread thread1 = new Thread(printA);
    Thread thread2 = new Thread(print100);

    thread1.start();
    thread2.start();
  }
}

class PrintChar implements Runnable {
  private char charToPrint;
  private int times;

  public PrintChar(char c, int t) {
    charToPrint = c;
    times = t;
  }

  @Override
  public void run() {
    String fileName = "out.txt";
    try {
      synchronized (Multithread.class) {//to writ by one thread 
        FileWriter fw = new FileWriter(fileName, true);
        BufferedWriter bw = new BufferedWriter(fw);
        PrintWriter outputStream = new PrintWriter(bw);
        for (int i = 0; i < times; i++) {
          outputStream.print(charToPrint);
        }
        outputStream.close();
      }
    }
    catch (IOException e) {
      e.printStackTrace();
    }
  }
}

class PrintNum implements Runnable {
  private int lastNum;

  public PrintNum(int n) {
    lastNum = n;
  }

  @Override
  public void run() {
    String fileName = "out.txt";
    try {
      synchronized (Multithread.class) {//to write by one thread
        FileWriter fw = new FileWriter(fileName, true);
        BufferedWriter bw = new BufferedWriter(fw);
        PrintWriter outputStream = new PrintWriter(bw);
        for (int i = 1; i <= lastNum; i++) {
          outputStream.print(" " + i);
        }
        outputStream.close();
      }
    }
    catch (IOException e) {
      e.printStackTrace();
    }
  }
}