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Summary of I / O knowledge points

2022-04-23 02:04:00 【Fu Sheng Ruo Meng 521】

I/O Flow of knowledge

		·I/O The basic concept of
		·I/O Application of stream knowledge
		· A practical example

		Basic knowledge of , What is flow

		· Simply speaking , Stream is a unified management of data input and output .
		· The system helps us define how to write the contents of the stream to different external devices , When programming , All we need to consider is how to write the data in memory to the stream
		· Determination of the direction of flow ：

		The reference is our own memory space
		· Output stream ：FileOutputStream, Is to store memory space data Write To external devices
		· Input stream ：FileInputStream, Is to transfer external data read Into memory .

		· The output stream is write
		· The read stream is the input stream


		The type of flow
		· Character stream , Is to transmit in character units , Character streams can be processed directly Unicode But it can only handle characters or strings
		· Byte stream , Is to transmit in bytes , Byte stream can be used for any object , But you can't deal with it directly Unicode character

		When to use what stream
		· If you're dealing with plain text , Then use the character stream
		· If it's dealing with pictures 、 Video etc. , Then use byte stream

		Byte stream
		· Byte stream operations are inherited from abstract classes
		InputStream And OutputStream

		· Generally, you can operate on files , Will use
		FileInoutStream And FileOutputStream



		·FileIutputStream Input stream

		String path = "D:/test.txt";
		File file = new Path();
		FileInputStream fis = new FileInputStream(file);
		if(!file.exists()){
		// If not, create a file
		file.createNewFile();
		}

		//1024 Is the maximum space that can be created , To avoid not knowing how big the file is
		byte[] in = new byte[1024];

		// Read the contents of the file
		fis.read(in);
		System.out.prinln(new String(in));



		·FileOutputStream Output stream

		String path = "D:/test.txt";
		File file = new Path();
		if(!file.exists()){
		// If not, create a file
		file.createNewFile();
		}
		FileOutputStream fos = new FileOutputStream(file);
		byte[] out = {'1','2','3'};
		fos.write(out);


		· If you want to save objects , You can use
		ObjectInputStream And ObjectOutputStream

		· among ,input Indicates input , Read ;output Identify the output , The write ;

		· Operations on objects ObjectInputStream And ObjectOutputStream



		Character stream
		· Character stream operations inherit from abstract classes
		Reader And Writer
		· Generally operate on files , Will use FileReader And FileWriter



		How to improve byte stream efficiency
		·BufferedInputStream And BufferedOutputStream
		· Because the byte stream is through byte To transmit , and byte The maximum transmission is 1024,1024byte=1kb, The file transferred is very small , So how do we optimize it ,
		Then we need to use BufferedInputStream And BufferedOutputStream To transmit ,byte It's similar to that every time we transmit, it's in bytes , It's like a string,
		Then through the String【】 Every time we transmit an array, we transmit it group by group , therefore Buffered That's how it works , We go through Buffered The blessing , We are a group byte A group of byte The transmission of .

		InputStream is = new FileInputStream(sourcePath);
		BufferedInputStream bis = new BufferedInputStream(is);

		OutputStream os = new FileOutputStream(desPath);
		BufferedOutputStream bos = new BufferedOutputStream(os);

		byte[] in = new byte[1024];

		int count= 0;
		while ((count = bis.read(in)) != -1) {
		bos.write(in, 0, count);
		}
		bis.close();
		bos.close();

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本文为[Fu Sheng Ruo Meng 521]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/04/202204220842001974.html

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