Java 为什么我们使用system.out.flush()？
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why we use system.out.flush()?
提问by Ali Kashanchi
Can someone please explain why we we would use system.out.flush()in a simpler way? If there could be a chance of losing data, please provide me with an example. If you comment it in the code below nothing changes!
有人可以解释为什么我们会system.out.flush()以更简单的方式使用吗？如果可能会丢失数据，请提供一个示例。如果您在下面的代码中对其进行注释，则没有任何变化！
class ReverseApp{
public static void main(String[] args) throws IOException{
String input, output;
while(true){
System.out.print("Enter a string: ");
System.out.flush();
input = getString(); // read a string from kbd
if( input.equals("") ) // quit if [Enter]
break;
// make a Reverser
Reverser theReverser = new Reverser(input);
output = theReverser.doRev(); // use it
System.out.println("Reversed: " + output);
}
}
}
Thank you
谢谢
采纳答案by SegFault
When you write data out to a stream, some amount of buffering will occur, and you never know for sure exactly when the last of the data will actually be sent. You might perform many operations on a stream before closing it, and invoking the flush() method guarantees that the last of the data you thought you had already written actually gets out to the file.
当您将数据写入流时，会发生一定量的缓冲，并且您永远无法确切知道最后一个数据何时实际发送。您可能会在关闭流之前对它执行许多操作，并且调用 flush() 方法可确保您认为已经写入的最后一个数据实际上已到达文件中。
Extract from Sun Certified Programmer for Java 6 Exam by Sierra & Bates.
摘自Sierra & Bates 的 Sun 认证程序员 Java 6 考试。
In your example, it doesn't change anything because System.outperforms auto-flushing meaning that everytime a byte in written in the buffer, it is automatically flushed.
在您的示例中，它不会更改任何内容，因为System.out执行自动刷新意味着每次写入缓冲区的字节都会自动刷新。
回答by Rogue
You use System.out.flush() to write any data stored in the out buffer. Buffers store text up to a point and then write when full. If you terminate a program without flushing a buffer, you could potentially lose data.
您使用 System.out.flush() 写入存储在输出缓冲区中的任何数据。缓冲区将文本存储到一个点，然后在满时写入。如果在不刷新缓冲区的情况下终止程序，则可能会丢失数据。
回答by Anton Dozortsev
Here is what the say documentation.
这就是说文档的内容。
