首先，在执行读操作时，一旦没有写者，读者会进入写者临界区writerCritical.enterCriticalSection()，直到最后读者人数等于0时，离开写者临界区，因此，写者执行写操作，进入写者临界区时，需等待，直到没有读者为止；其次，每个写者进行写操作时，必须首先进入写者临界区，而synchronized关键字定义的方法，使得同一时间同步方法不允许被多次调用，这就保证了不可能有两个写者同时工作。所以，只允许一个写着对文件执行写操作。-First, perform a read operation, if they are not writers, readers who write critical region will enter writerCritical.enterCriticalSection (), until the last readership is equal to zero, leaving writers critical region, therefore, writing to execute a write operation, enter the write those critical areas, the need to wait until there are no readers so far　Second, each writer to write, you must first enter the critical section writer, and synchronized keyword defined methods, making at the same time synchronization method allowed to be repeated call, which guarantees not have two write work simultaneously. Therefore, only one written on the file for write access.