1, InputStream and FileInputStream

InputSteam is an abstract class, which cannot be instantiated. It is a super class representing all classes of Byte input stream. All streams inherited from InputSteam are used to input data (read) into the program, and the unit of data is Byte (English Byte, short for B).

Common methods:

FileInputStream reads files in byte mode, suitable for reading all types of files (image, video, text files, etc.). As like as two peas in InputStream, the common method of FileInputStream is not understood, and the level is not enough.

Test it:

package cn.zjb.test;

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

/**
 * Test file input byte stream
 * @author Zhang Jian Bo
 *
 */
public class TestInputStream {
	
	private static FileInputStream in;
	private static final int DEFAULT_CAPACITY=1024; 
	
	private static void printContent1(String src) throws IOException {
		/*
		 * Known byte size in file
		 */
		in=new FileInputStream(src); 
		for(int i=0;i<10;i++)
			System.out.print(in.read()+" ");
		System.out.println();
		in.close();  //If it is not closed, there may be errors. Be sure to close the corresponding stream
		
	}
	
	private static void printContent2(String src) throws IOException{
		/*
		 * Whether you know the number of bytes in the file or not
		 */
		in=new FileInputStream(src);
		int temp;
		while((temp=in.read())!=-1)
			System.out.print(temp+" ");
		System.out.println();
		in.close();
		
	}
	
	private static void printContent3(String src) throws IOException {

		in=new FileInputStream(src); 
		byte[] buffer=new byte[DEFAULT_CAPACITY];
		in.read(buffer);
		for(int i=0;buffer[i]!=0;i++) 
			System.out.print(buffer[i]+" ");
		System.out.println();
		in.close();
		
	}
	
	private static void printContent4(String src) throws IOException {

		in=new FileInputStream(src); 
		byte[] buffer=new byte[DEFAULT_CAPACITY];
		/*
		in.read(buffer,2,5);
		for(int i=0;buffer[i]!=0;i++) 
			System.out.print(buffer[i]+" ");  //No output
 		for(int i=0;i<DEFAULT_CAPACITY;i++) 
			System.out.print(buffer[i]+" ");  //Operation result: 0.072 101 108 108 111 0.000···
		*/
		in.read(buffer,0,2);
		for(int i=0;buffer[i]!=0;i++) 
			System.out.print(buffer[i]+" ");
		System.out.println();
		in.close();
		
	}
	
	public static void main(String[] args) throws IOException {
		printContent1("D:\\a.txt"); //a. The content of the txt file is: Hello Java
		printContent2("D:\\a.txt");
		printContent3("D:\\a.txt");
		printContent4("D:\\a.txt");
	}
}

2, OutputStream and FileOutputStream

OutputStream is an abstract class that is the parent of all classes representing byte output streams. The output stream receives the output bytes (writes) and sends them to a destination.

Common methods:

FileOutputStream writes data to files in bytes, suitable for all types of files.

Construction method:

The common methods of FileOutputStream and OutputStream are the same.

Test it:

package cn.zjb.test;

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

/**
 * Application of test byte output stream
 * @author Zhang Jian Bo
 *
 */
public class TestOutputStream {
	
	private static FileOutputStream out;
	private static final String src="D:\\a.txt";
	private static final byte[] buffer= {104,97,110,103}; // hang
	
	private static void writeInTxt1(String src) throws IOException {
		
		out=new FileOutputStream(src);
		out.write(122); //'z'
		out.close();
	}
	
	private static void writeInTxt2(String src) throws IOException {
		
		out=new FileOutputStream(src,true); //Append at the end of source file
		out.write(buffer); 
		out.close();
	}
	
	public static void main(String[] args) throws IOException {
		writeInTxt1(src);  //Run first
		writeInTxt2(src);
	}
	
}
}

3, Reader and FileReader

Reader is an abstract class, which is used to read character stream abstract class. The data unit is character. In Unicode, a character is equal to two bytes, that is, a 16 bit binary number.

Common methods:

The common methods of FileReader are the same as those in FileReader. Test the following:

package cn.zjb.test;

import java.io.FileReader;
import java.io.IOException;

/**
 * Test character input stream
 * @author Zhang Jian Bo
 *
 */
public class TestFileReader {
	
	private static FileReader read;
	private static final String src="D:\\a.txt"; //zhang

	private static void readFile(String src) throws IOException {
		read=new FileReader(src);
		System.out.println(read.read());
		read.close();
	}
	
	public static void main(String[] args) throws IOException {
		readFile(src); //122
	}
}

4, Writer and FileWriter

Writer is an abstract class, which is used to write character stream abstract class. The data unit is character.

Common methods:

FileWriter construction method:

The common methods of FileWriter are the same as those in FileWriter. Test them as follows:

 package cn.zjb.test;

import java.io.FileWriter;
import java.io.IOException;

/**
 * Test character output stream
 * @author Zhang Jian Bo
 *
 */
public class TestFileWriter {

	private static FileWriter fw;
	private static final String src="D:\\a.txt";
	private static final char[] buffer= {122,104,97,110,103,0x5f20};  //zhang Zhang
	
	private static void writeFile1(String src) throws IOException {
		fw=new FileWriter(src); //cover
		fw.write(122);
		fw.close();
	}
	
	private static void writeFile2(String src) throws IOException {
		fw=new FileWriter(src,true); //Add to
		fw.write(buffer);
		fw.close();
	}
	
	public static void main(String[] args) throws IOException {
		writeFile1(src); //Run first
		writeFile2(src);
	}
	
}