Character stream
Character stream overview
Character stream: only character files in the computer can be operated
/ / file copy case: regardless of file type, use byte stream!
/ / when operating character files, byte stream will be inconvenient, so it is recommended to use character stream
/ / character file: open it with the Notepad tool of windows
The essence of character stream: the bottom layer is byte stream, but it is highly encapsulated! / / the character stream is a wrapper stream with a buffer
Character stream = byte stream + encoding format;
/ / the output content of the character output stream needs to refresh the buffer!!
Root node of character stream: reader/writer - > abstract class
Ordinary character stream: filewriter/filereader - > not commonly used, inefficient
Efficient character stream: bufferedwriter / BufferedReader - > common, high efficiency
FileWriter/FileReader
FileWriter/FileReader: normal character stream
FileWriter: file character output stream
Construction method:
FileWriter(String fileName) //Target file FileWriter(File file) //Write with append: FileOutputStream/FileWriter FileWriter(String fileName, boolean append) FileWriter(File file, boolean append)
How to write:
Write one character at a time : void write(int ch) Write one character array at a time : void write(char[] chs) Write part of a character array one at a time : void write(char[] chs,int offset,int length) Write one string at a time : void write(String str) Write one part of a string at a time : void write(String str,int offset,int length)
FileReader: file character input stream
Construction method:
FileReader(String fileName) //source file FileReader(File file) //source file
How to read:
Read one character at a time : int read() Read one character array at a time : int read(char[] chs) Read part of a character array one at a time : int read(char[] chs,int offset,int length) //There is no way to read one string at a time
Standard code
Common character streams copy character files one character at a time:
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class Common character stream copy character file one character at a time {
public static void main(String[] args) throws IOException {
//Create stream
FileWriter fw = new FileWriter("Destination file address");
FileReader fr = new FileReader("Source file address");
//Cyclic read / write
int ch;//Store one character read at a time
while((ch = fr.read()) != -1){
//Read one character and write one character
fw.write(ch);
//Manual refresh
fw.flush();
}
//Closed flow
fw.close();
fr.close();
}
}Common character streams copy character files one character array at a time:
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class Ordinary character stream copy character file one character array at a time {
public static void main(String[] args) throws IOException {
//Create stream
FileWriter fw = new FileWriter("Destination file address");
FileReader fr = new FileReader("Source file address");
//Cyclic read / write
char[] chs = new char[1024];
int len;//Count the number of characters read each time
while ((len = fr.read(chs)) != -1){
//Write as much as you read
fw.write(chs,0,len);
//Refresh
fw.flush();
}
//Closed flow
fw.close();
fr.close();
}
}BufferedWriter/BufferedReader
BufferedWriter/BufferedReader: efficient character output / character input stream (automatically refreshed buffer)
Construction method:
BufferedWriter(Writer writer)
BufferedReader(Reader reader)
General reading and writing methods:
How to write:
Write one character at a time : void write(int ch) Write one character array at a time : void write(char[] chs) Write part of a character array one at a time : void write(char[] chs,int offset,int length) Write one string at a time : void write(String str) Write one part of a string at a time : void write(String str,int offset,int length)
How to read:
Read one character at a time : int read() Read one character array at a time : int read(char[] chs) Read part of a character array one at a time : int read(char[] chs,int offset,int length) //There is no way to read one string at a time
Standard code
Efficient character stream copy character files one character at a time:
import java.io.*;
public class Efficient character stream copy character files one character at a time {
public static void main(String[] args) throws IOException {
//Create stream
BufferedWriter bw = new BufferedWriter(
new FileWriter("Destination file address"));
BufferedReader br = new BufferedReader(
new FileReader("Source file address"));
//Cyclic read / write
int ch;//Store one character read at a time
while((ch = br.read()) != -1){
//Read one character and write one character
bw.write(ch);
}
//Closed flow
bw.close();
br.close();
}
}Efficient character stream copy character files one character array at a time:
import java.io.*;
public class Efficient character stream copy character files one character array at a time {
public static void main(String[] args) throws IOException {
//Create stream
BufferedWriter bw = new BufferedWriter(new FileWriter("Destination file address"));
BufferedReader br = new BufferedReader(new FileReader("Source file address"));
//Cyclic read / write
char[] chs = new char[1024];
int len;//Count the number of characters read each time
while ((len = br.read(chs)) != -1){
//Write as much as you read
bw.write(chs,0,len);
}
//Closed flow
bw.close();
br.close();
}
}Efficient character stream copy character files one line at a time:
import java.io.*;
public class Efficient character stream copy character files one line at a time {
public static void main(String[] args) throws IOException {
//Create stream
BufferedWriter bw = new BufferedWriter(
new FileWriter("Destination file address"));
BufferedReader br = new BufferedReader(
new FileReader("Source file address"));
//Cyclic read / write
String line;//To store a row of data read each time
while((line = br.readLine()) != null){
//Read and write one line
bw.write(line);
//Fill in line breaks
bw.newLine();
}
//Closed flow
bw.close();
br.close();
}
}Coding format
Encoding and decoding
Code: binary code (01010101110011) - > bytes in hard disk - > file (character file)
Coding: write binary code (text -- > binary code) - > > from understandable to incomprehensible
Decoding: parsing binary code (binary code -- > text) - > > from incomprehensible to understandable
The problem of file garbled
Coding: write binary code (text - (in what way) - > binary code) - > > from understandable to incomprehensible
Decoding: parsing binary code (binary code - (how to solve) - > text) - > > from incomprehensible to understandable
How to compile / solve: coding format (coding table)
The root cause of garbled Code: inconsistent encoding and decoding methods
Solution to file garbled Code: modify the coding format of the file to be consistent with that of the platform!!!
Coding table
Code table: the "codebook" between byte and text conversion// If the "codebook" of encoding and decoding is inconsistent, it will be garbled!
Character set: there are multiple sets of coding tables in a character set;
The most basic character set: ASCII (American standard information exchange code table) - > can only solve the language coding problem in English environment
/ / English letters and numbers will not be garbled. The first 128 bits of all coding tables are ASCII
Chinese character set: GB series (National Standard Series)
GB2312: early Chinese coding table
GBK: the most commonly used Chinese coding table now
//GBK uses 2 bytes to represent a Chinese character
"International Organization for unity": unified the coding format of the World Wide Web
Designed a character set: Unicode character set
UTF-8 coding table: unified coding format of Internet data;
//UTF-8 encoding table uses 3 bytes to represent a Chinese character
UTF-16
UTF-32
ANSI: it is not a coding table -- > local character set: windows system will automatically switch the coding format represented by ANSI local character set according to time zone and system language;
ANSI = default character set of the current computer;