The difference between FileInputStream and bufferedinputstream

Java Standard library java.io.InputStream Defines the superclass of all input streams ：

FileInputStream File stream input is realized ;

BufferedInputStream Use buffer to improve the efficiency of file reading ;

ByteArrayInputStream Simulate a byte stream input in memory ;

One . FileInputStream（ File input stream ）

FileInputStream yes InputStream Subclasses of , Is to read data from the file stream , Every read is from the hard disk , Slow read speed ;

InputStream Pass through read() Method to read the next byte of the input stream , And return the... Represented by bytes int value (0 ~ 255), If you read -1 You can't continue reading ;

InputStream Buffer read ： So let's define one byte[] Array as buffer ,read() Method will read as many bytes as possible into the buffer , But it won't exceed the size of the buffer .

Read once using buffer InputStream All bytes of ( The two methods )：

(1)  Read byte by byte ;（2） Bulk read .

The code implementation is as follows ：

try (InputStream in = new FileInputStream("D:\\countNumber.text")) {
             //  The way 1： Read byte by byte 
//		int data = -1;
//		while((data = in.read()) != -1) {
//			System.out.println((char)data);
//		}
			//  The way 2： Bulk read 
			byte[] buff = new byte[1000]; //  Definition 1000 Byte size buffer 
			int size = -1;
			while((size = in.read(buff)) != -1) {
				System.out.println();
			}
		} catch (IOException e1) {
			e1.printStackTrace();
		}
		
		

Two . BufferedInputStream( Buffered input stream )

BufferedInputStream Is a buffered input stream ( Byte input stream with buffer ), Inherited from FilterInputStream( yes InputStream Subclasses of ), The function is to add some functions to another input stream ： Provide buffer function and support “mark() Mark ”,“reset() Reset method ";

BufferedInputStream The essence is realized through an internal buffer array , It has a default size of 8192 The buffer ( Read faster ). for example , Create an input stream corresponding to BufferedInputStream after , When we go through read() When reading data from the input stream ,BufferedInputStream The data of the input stream will be filled into the buffer in batches . Every time the data in the buffer is read , The input stream fills the data buffer again ; So again and again , Until we finish reading the input stream data location .

public class BufferedInputStream extends FilterInputStream {

    private static int DEFAULT_BUFFER_SIZE = 8192;
    ...}

			try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream("D:\\countNumber.text"))) {
			//  The way 1： Read byte by byte 
			// int data = -1;
			//while((data = bis.read()) != -1) {
		//		System.out.println(data);
		//	}
			//  The way 2： Bulk read 
			byte[] buffData = new byte[128]; //  Used to store the byte array read each time 

			int len = -1; //  The length of the byte array read each time 
			while((len = bis.read(buffData)) != -1) {
				System.out.println(Arrays.toString(buffData));
			}
		} catch (IOException e) {
			e.printStackTrace();
		} 

  notes ： If a file is opened for reading and writing , Close it in time after completion , In order to make os Release resources (try sentence ： Shortcut key ：shift+alt+z, The compiler will automatically write finally And call close（）), actually , The compiler is not specifically for InputStream Plus automatic shutdown , But because it realizes AutoCloseable Interface , Thanks to the implementation of this interface , Will be written automatically finally And call close（）;