Write of FileInputStream class and read of fileoutstream class

Byte stream

preface: have you ever thought about the videos we usually watch,
In what form are audio and pictures stored What form are they stored?

---

Byte streamThere are two kinds. One isoutputOne isinputHere are allOutput input streamThe top-level parent of.

---

Byte output stream：OutputStream
Byte input stream：InputStream

---

Fileoutputstream class（Output class)

Subclass of output stream FileOutputStreamClass is a file output stream

closeMethod: close the resources released by this stream. Don’t waste memory.
writeMethods (there are three uses) let me show you:

---

package com.kjzz.pojo;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

public class day1 {
    public static void main(String[] args) throws IOException {
        // a 
        File file = new File("A.txt");
        FileOutputStream fos = new FileOutputStream(file);
        //The first is to write out data
        fos.write(97); // a 
        fos.write(98); // b
        //Close resource
        fos.close();

        // b
        FileOutputStream fo= new FileOutputStream("B.txt");
        //Second byte array
        Byte [] B = "can you think no" getBytes();
        fo. write(b); //  Can you think no
        //Close resource
        fo.close();

        // c
        //Create a stream object with a file name
        FileOutputStream f = new FileOutputStream("C.txt");
        byte [] c = "abQAQ".getBytes();
        //The third option is to select three numbers after two subscripts in the byte array di2
        f.write(c,2,3); // QAQ
        //Close resource
        f.close();
        
    }
}

summary：1. Remember to use when the stream operation is completedClose methodFree system memory. 2. The third usage of writeThe second is the subscriptThe third is choicebehindA few digits.

---

Is fileoutstream dataTracing + Line feed operationHow do you use it?

1. Whether to append is to add false (default) to fileoutstream.

2. Line feed operation in Windows system\r\nIt’s a line break

import java.io.FileOutputStream;
import java.io.IOException;

public class day2 {
    public static void main(String[] args) throws IOException {

        FileOutputStream fos = new FileOutputStream("AA.txt",true);

        byte [] b = "abc".getBytes();
        
        fos.write(b);
        fos.write("\r\n".getBytes());
       
        //Close resource
        fos.close();
        
    }
}
Output results:
ABC (pay attention to line feed)
ABC (secondary operation)
ABC (three runs)

---

FileInputStream class (input class)

Is a file input stream that reads bytes from the file.

His method:

read ：Byte array read data

import java.io.FileInputStream;
import java.io.IOException;

public class day3 {
    public static void main(String[] args) {
        try {
            //Create stream object with file name
            FileInputStream fis= new FileInputStream("BB.txt");
            //Define variable as a valid unit 0
            int len;
            //Select unit 
            byte [] b = new byte [2];
            
            while ( (len = fis.read(b)) != -1 ) {
                System.out.println(new String(b,0,len));
            }
            
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}
Output results:
ab
cd
e

summary: select a constant of 0 and use the while loop.

InputStream output stream (read) OutputStream input stream (write).