实现父子进程的同步，当父进程试图从一空管道中读取数据时，便进入等待状态，直到子进程将数据写入管道返回后，才将其唤醒。
Son process to achieve the synchronization, when the parent tried to read an empty pipe, they enter the wait state until the child process to write data pipeline to return only after its wake.
当一个方法被选中(单击)，它就展开并显示父子节点，背景色为紫色的是父节点，背景色为黄色的是子节点。
When a method is selected (by clicking on it), it expands to show the parents and children. Parents are shown with a purple background and children with a yellow background.
当一个方法被选中(单击)，它就展开并显示父子节点，背景色为紫色的是父节点，背景色为黄色的是子节点。
When a method is selected (by clicking on it), it expands to show the parents and children. Parents are shown with a purple background and children with a yellow background.
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