java - 我需要在那里显式使用 flush() 方法吗？

Question

我需要在那里明确writer.flush()或不？我想离开后save()方法 writer可能无法将数据写入 outputStream

import java.io.*;

public class Test
{
    public int i = 5;
    
    public void save(OutputStream outputStream) throws Exception
    {
        PrintWriter writer = new PrintWriter(outputStream);
        writer.println(i);
        writer.flush(); // necessarily or not?
    }
}

Answer 1

来自 flush文档:

 /**
  * Flushes the stream.  If the stream has saved any characters from the
  * various write() methods in a buffer, write them immediately to their
  * intended destination.  Then, if that destination is another character or
  * byte stream, flush it.  Thus one flush() invocation will flush all the
  * buffers in a chain of Writers and OutputStreams.
  *
  * <p> If the intended destination of this stream is an abstraction provided
  * by the underlying operating system, for example a file, then flushing the
  * stream guarantees only that bytes previously written to the stream are
  * passed to the operating system for writing; it does not guarantee that
  * they are actually written to a physical device such as a disk drive.
  *
  * @throws java.io.IOException
  *          If an I/O error occurs
  */

因此，如果您需要保证将字节写入下一个流，请调用它。
请看 checkError根据其文档:

* Flushes the stream if it's not closed and checks its error state.