27io stream, byte output stream, OutputStream writes data to file

Hard disk permanent storage , The data stored in the hard disk is bytes 、 Memory ： Temporary storage

IO summary

I:input( Input )  Read

O：output（ Output ） write in

flow ： data （ character 、 byte ） 1 Characters =2 Bytes =8 Binary bits

Input ： It is to read the data in the hard disk into the memory for use

Output ： Write the data in memory to the hard disk to save

According to the data, it is divided into ： Character stream 、 Byte stream

Byte stream ： Byte input stream ：InputStream Byte output stream ：OutputStream

Character stream ： Character input stream ：Read        Character output stream ：Writer

Byte stream ：

Everything is bytes ：

All file data （ Text 、 Images 、 video ） In storage , Are stored in binary form , It's all a byte , So it's the same when it's transmitted , So byte stream can transfer any file data , When operating the flow , We need to be clear at all times , No matter what flow object is used , The underlying transmission is always binary data

Byte output stream OutputStream

Java.io.OutputStream This abstract class is a superclass that represents all classes of all output streams （ Parent class ） Write the specified byte information to the destination

Method ：

close（） Close this output stream and release all system resources related to this stream

flush（） Refresh the output stream once and force all buffered output bytes to be written out

write（） Yes 3 individual   Write data to hard disk

  write（byte[] b） take b.length Bytes from specified Of byte Array Write this output stream

public void' write(byte[] b): take b.length Byte writes this output stream from the specified byte array 
   If the first byte written is a positive number （0-127）, Then the display will query ASCII surface 
   If the first byte written is negative , The first byte and the second byte will form a Chinese display , Query the system default code table （GBK）

  write（byte[] b,int off,int len ） Writes the specified byte array to len Bytes , From the offset off Start the output stream to this

 public void write（byte [] b,int off,int len）: Write part of the byte array to a file 
   int off： Start index of array 
   int len： Write a few bytes 
    The specified byte array is written len byte , From the offset off Start output to this output stream 

  write（int b） Output the specified byte stream   Write a byte

Directly known subclass ：ByteArrayOutputStream、FileOutputStream、FilterOutputStream ObjectOutputStream、OutputStream、PipeOutputStream

FileOutputStream File byte output stream effect ： Write the data in memory to a file

Construction method ：

  FileOutputStream（String name） Create a file with the specified name Output file stream for writing data

  FileOutputStream（File file） Create a File Object to write data in the file represented by File output stream

Parameters ： The destination where the data is written

  String name： The destination is the path of a file

  File file ： The destination is a file

The function of construction method ：

1. Create a FileOutputStream object
2. According to the file passed in the constructor / File path , Create an empty file
3. Will be able to FileOutputStream Object points to the created file

The principle of writing data ：（ Memory - Hard disk ）

Java Program —>JVMàOS（ operating system ）àOS（ Own method ） Call the method that writes the data à Write data to a file

The steps of using byte output stream ：

1. Create a FileOutputStream object , The destination to which the data is to be written in the constructor
2. call FileOutputStream Object write Method to write data to a file
3. Release resources （ Stream usage will occupy the memory of the hardtop , Empty the memory after use , Improve the efficiency of the program ）

fos.write(97);// When writing data , Will be able to 10 Hexadecimal integer 97, Convert to binary integer

The data stored in the hard disk is bytes

Any text editor （ Notepad ） When you open the file again , Will look up the code table , Convert bytes to character representation

0-127 Inquire about ASCII surface

See the system default code table for other values （ Chinese system GBK）

Detailed code : Write data to computer memory E:\\ Multithreading \\a.txt

package demo27 Byte output stream writes data to file ;
/*
    Construction method ：
  FileOutputStream（String name） Create an output file stream that writes data to a file with the specified name 
  FileOutputStream（File file） Create a File Object represents the file output stream in which data is written 
 Parameters ： The destination where the data is written 
  String name： The destination is the path of a file 
  File file ： The destination is a file 
 The function of construction method ：
1.	 Create a FileOutputStream object 
2.	 According to the file passed in the constructor / File path , Create an empty file 
3.	 Will be able to FileOutputStream Object points to the created file 

 */

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

public class DemoOutputStream {
    public static void main(String[] args) throws IOException {
        //1. Create a FileOutputStream object , The destination to which the data is to be written in the constructor 
        FileOutputStream fos=new FileOutputStream("E:\\ Multithreading \\a.txt");//FileOutputStream There are exceptions that need to be thrown 
        //2. call FileOutputStream Object write Method to write data to a file 
        fos.write(97);// When writing data , Will be able to 10 Hexadecimal integer 97, Convert to binary integer 
        //3. Release resources （ Stream usage will occupy the memory of the hardtop , Empty the memory after use , Improve the efficiency of the program ）
        fos.close();
    }
}

result ：

E:\\ At the beginning of multithreading ：

After running the code ：