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生产者消费者问题(5) – Java多进程实现？

发现就是个坑，Java的多进程无论是ProcessBuild还是Runtime，都是cmd启动另一个进程，虽然父进程可以从子进程拿到IO流，但是又有什么用呢？照样没法实现同步互斥。Java进程间通信没有管道，没有共享内存，难道要我用共享文件，可是共享文件本身就存在同步互斥问题。于是只好放弃。

以下的代码并没有解决生产者消费者问题，只是我用FileLock的探索，加上该死的IO流。

importjava.io.BufferedReader; importjava.io.IOException; importjava.io.InputStream; importjava.io.InputStreamReader;   public class ProcessLauncher {  public static void main(String[] args) {  ProcessLauncherlauncher = new ProcessLauncher();    int p = 0;  int c = 0;    if (args.length != 2) {  System.out.println("please input /"ConditionLauncher [p] [c]/"");  return;  }    try {  p = Integer.parseInt(args[0]);  c = Integer.parseInt(args[1]);  } catch (NumberFormatException e) {  e.printStackTrace();  }    try {  for (int i = 0; i < p; i++) {  ProcessBuilderproducerBuilder = new ProcessBuilder();  producerBuilder.command("java", "Producer", i + "");  producerBuilder.redirectErrorStream();  Processprocess = producerBuilder.start();    launcher.newOutputThread(process.getInputStream()).start();  }    for (int i = 0; i < c; i++) {  ProcessBuilderconsumerBuilder = new ProcessBuilder();  consumerBuilder.command("java", "Consumer", i + "");  consumerBuilder.redirectErrorStream();  Processprocess = consumerBuilder.start();    launcher.newOutputThread(process.getInputStream()).start();  }  } catch (IOException e) {  e.printStackTrace();  }  }    // 用来打印子进程的输入流  class OutputThread extends Thread {  private InputStreaminput;    public OutputThread(InputStreaminput) {  this.input = input;  }    @Override  public void run() {  try {  BufferedReaderreader = new BufferedReader(new InputStreamReader(input));  String tempString = null;  while ((tempString = reader.readLine()) != null) {  System.out.println(tempString);  }  } catch (IOException e) {  e.printStackTrace();  }  }  }   }

消费者

importjava.io.BufferedWriter; importjava.io.File; importjava.io.FileOutputStream; importjava.io.IOException; importjava.io.OutputStreamWriter; importjava.nio.channels.FileLock;   public class Consumer {    public static void main(String[] args) {  String processName = "Consumer " + args[0];    FileLocklock = null; // 文件锁    BufferedWriterout = null;    while (true) {  try {  Filefile = new File(Util.PATH);  if (!file.exists())  file.createNewFile();  int num = Integer.parseInt(Util.readFile());    try {  Thread.sleep(500);  } catch (InterruptedExceptione1) {  // TODO Auto-generated catch block  e1.printStackTrace();  }    System.out.println(processName + ":" + num);    if (num == 0)  continue;    try {  if (!file.exists())  file.createNewFile();  FileOutputStreamoutput = new FileOutputStream(file);  OutputStreamWriterwriter = new OutputStreamWriter(output);    lock = output.getChannel().lock();    out = new BufferedWriter(writer);    System.out.println(processName + ": " + num + " -> " + (num - 1));    out.write((num - 1) + "");  out.flush();  } catch (IOException e) {  e.printStackTrace();  } finally {  if (lock != null) {  lock.release();  }  if (out != null) {  out.close();  }  }  } catch (IOException e) {  e.printStackTrace();  }  }  }   }

生产者

importjava.io.BufferedWriter; importjava.io.File; importjava.io.FileOutputStream; importjava.io.IOException; importjava.io.OutputStreamWriter; importjava.nio.channels.FileLock;   public class Producer {    public static void main(String[] args) {  String processName = "Producer " + args[0];    FileLocklock = null; // 文件锁    BufferedWriterout = null;  while (true) {  try {  Filefile = new File(Util.PATH);  if (!file.exists())  file.createNewFile();    int num = Integer.parseInt(Util.readFile());    try {  Thread.sleep(500);  } catch (InterruptedExceptione1) {  // TODO Auto-generated catch block  e1.printStackTrace();  }    System.out.println(processName + ":" + num);    if (num == Util.MAX_SIZE)  continue;    try {  if (!file.exists())  file.createNewFile();  FileOutputStreamoutput = new FileOutputStream(file);  OutputStreamWriterwriter = new OutputStreamWriter(output);    lock = output.getChannel().lock();    out = new BufferedWriter(writer);    System.out.println(processName + ": " + num + " -> " + (num + 1));    out.write((num + 1) + "");  out.flush();  } catch (IOException e) {  e.printStackTrace();  } finally {  if (lock != null) {  lock.release();  }  if (out != null) {  out.close();  }  }    } catch (IOException e) {  e.printStackTrace();  }  }  }   }

发现实在搞不定以后，我转而去用Python实现，还是Python大法好。

原文 https://www.zhouchao.me/pv-java-multiprocess/

正文到此结束