Detailed explanation of the function and usage of flush () function in Java language

Recently, when I was learning IO streams, I found that the flush () function appears every time. After checking its functions, the main functions are as follows

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General and wrong answer:

The data in the buffer is not written out until the buffer is full. You can also use the flush method to force the data in the buffer to write out, or use the close () method to close the stream. Before closing the stream, the buffer output stream writes out the buffer data at one time. Both flash () and close () force the data to be written out, so the two results are the same. If you don't write, you will find that it can't be written out successfully

For the above answers, an accurate answer is given

Fileoutputstream inherits OutputStream and does not provide rewriting of flush() method. Therefore, no matter how much content is written, the binary stream will be directly passed to the I / O of the underlying operating system. Flush has no effect. However, the buffered series of I / O stream functions can be seen from the word buffered alone that they use buffers. The application program has to communicate with the device every IO, which is very inefficient, Therefore, in order to improve the efficiency of the buffer, when writing to the device, write to the buffer first. When there is enough data in the buffer, write to the device as a whole

Use bufferedxxxstream. The default buffer size is 8K. When reading, the buffer will always be filled (or the file is read). When writing, the content will not be sent to the kernel buffer until the buffer is full (or the flush operation is performed). The reason for high efficiency is to avoid falling into the kernel of the operating system every byte read (which is a time-consuming operation). For the specific code, please check the API yourself.

Then attach a question from Baidu.

Flush () means to force the contents of the buffer to be written out. Because of some mechanisms of the operating system, in order to prevent constant disk reading and writing, there is the concept of delayed writing (note that it should not be confused with frush() refresh), which is mainly used in io, that is, emptying the buffer data. Generally, when reading and writing the stream, the data is read into the memory first, and then written to the file, When you read the data, it does not mean that your data has been written, because some of it may remain in the memory buffer. At this time, if you call the close () method to close the read / write stream, this part of data will be lost, so you should flush () before closing the read / write stream..

Also on the web server, in order to prevent sending a message after writing a byte, there is a concept of buffer, such as 64K memory area. When the buffer is full, it is written to the disk at one time (or sent to the client browser).

The flush method is generally executed when the program is written. This is followed by the close method. For example:

In simple terms, the flush () method is to output all the contents stored in memory (bulk output). Commonly used in FileWriter class is a typical example. In addition to using flush output, the last call close method will also batch output.

summary

The above is all about the detailed explanation of the function and use method of flush function in Java language. I hope it will be helpful to you. Interested friends can continue to refer to other related topics on this site. If there are deficiencies, please leave a message to point out. Thank you for your support!