我正在尝试编写一个脚本，该脚本将使用不同的参数运行4次.exe程序。我为每个.exe运行创建了一个线程。每个线程将写入一个输出文件。我的问题是，它应该并行写入，但是正如您在下面的屏幕快照中所见，该文件一个接一个地写入。应该如何解决？

这是主要方法：

public static void main (String args[]) {
    ExecutorService executor = Executors.newFixedThreadPool(4);
    executor.execute(new RunnableReader("myprogram.exe",param1,outputFile1));
    executor.execute(new RunnableReader("myprogram.exe",param2,outputFile2));
    executor.execute(new RunnableReader("myprogram.exe",param3,outputFile3));
    executor.execute(new RunnableReader("myprogram.exe",param4,outputFile4));
    executor.shutdown();
}

这是可运行的类：

public class RunnableReader implements Runnable {
    private String program;
    private String param;
    String outputFile;

    public RunnableReader(String program,String param,String outputFile) {
        this.program = program;
        this.param = param;
        this.outputFile = outputFile;
    }

    @Override
    public void run() {
        try {
            ProcessBuilder pb = new ProcessBuilder(program,param);
            pb.redirectOutput(ProcessBuilder.Redirect.PIPE);
            pb.redirectErrorStream(true);
            Process proc = pb.start();
            InputStream stream = proc.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(stream));
            BufferedWriter writer = new BufferedWriter(new FileWriter(outputFile,true));
            for(String output; (output = reader.readLine()) != null) {
                writer.append(output);
                writer.append("\n");
            }
            writer.close();
            reader.close();
            stream.close();
  
        } catch(IOException e) {
            e.printStackTrace();
        }
    }
}