OK，改个名字，只想知道第一题的详细答案，其他我也能说出一二，别鸡鸡爪爪的，没素质

请楼主说明到底是进程，还是线程哈。

是进程，当时我还正懵了，不过这个应该是他们项目中遇到的问题

对本次的面试感觉还是蛮惭愧的

多进程读写文件：一个进程A写文件file，另一个进程B读文件file
Doug Lea 在他的书中提供一个示例代码
ReadWrite 为抽象类，允许并发的读操作，不允许并发的写操作，也不允许读写同时进行。
可以扩展ReadWrite为SingleFileReadWrite 实现 doRead和doWrite方法来读写文件
线程A和线程B使用同一个SingleFileReadWrite 实例
SingleFileReadWrite rw;
threadB rw.read();
threadA rw.write();

abstract class ReadWrite {
 protected int activeReaders = 0;  // threads executing read
 protected int activeWriters = 0;  // always zero or one

 protected int waitingReaders = 0; // threads not yet in read
 protected int waitingWriters = 0; // same for write

 protected abstract void doRead(); // implement in subclasses
 protected abstract void doWrite();

 public void read() throws InterruptedException {
  beforeRead();
  try   { doRead(); }
  finally { afterRead(); }
 }

 public void write() throws InterruptedException {
  beforeWrite();
  try     { doWrite(); }
  finally { afterWrite(); }
 }
 protected boolean allowReader() {
  return waitingWriters == 0 && activeWriters == 0;
 }

 protected boolean allowWriter() {
  return activeReaders == 0 && activeWriters == 0;
 }

 protected synchronized void beforeRead()
  throws InterruptedException {
   ++waitingReaders;
   while (!allowReader()) {
    try { wait(); }
    catch (InterruptedException ie) {
      --waitingReaders; // roll back state
      throw ie;
    }
  }
  --waitingReaders;
  ++activeReaders;
 }

 protected synchronized void afterRead()  {
  --activeReaders;
  notifyAll();
 }

 protected synchronized void beforeWrite()
  throws InterruptedException {
   ++waitingWriters;
   while (!allowWriter()) {
    try { wait(); }
    catch (InterruptedException ie) {
     --waitingWriters;
     throw ie;
    }
   }
   --waitingWriters;
   ++activeWriters;
 }

 protected synchronized void afterWrite() {
  --activeWriters;
  notifyAll();
  }
}