我需要在那里显式使用 flush() 方法吗？

Question

我是否需要明确地writer.flush()或不需要？ 我认为离开save()方法后writer可能不会将数据写入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

从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，如果您需要保证字节被写入下一个 stream，请调用它。

请查看checkError根据其文档：

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