java_IO流小结

字符流和字节流的主要区别：

1.字节流读取的时候，读到一个字节就返回一个字节； 字符流使用了字节流读到一个或多个字节（中文对应的字节数是两个，在UTF-8码表中是3个字节）时。先去查指定的编码表，将查到的字符返回。

2.字节流可以处理所有类型数据，如：图片，MP3，AVI视频文件，而字符流只能处理字符数据。只要是处理纯文本数据，就要优先考虑使用字符流，除此之外都用字节流。



[b] 字节流：[/b]

1、通过字节流写数据

code：

package com.test;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

public class WriteByteStream {

public static void main(String[] args) {
try {

FileOutputStream fos = new FileOutputStream("textw.txt");
String outString = "write 123456写出数据";
byte output[] = outString.getBytes("UTF-8");
fos.write(output);
fos.close();

} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

}

2、通过字节流读数据：

code：

package com.test;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

public class ReadByteStream {

public static void main(String[] args) {
try {
FileInputStream fis = new FileInputStream("text.txt");
byte input[] = new  byte[21];
fis.read(input);

String inputString = new String(input, "UTF-8");
System.out.println(inputString);
fis.close();

} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

}

}

3、使用字节流读写数据

code：

package com.test;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class CopyByByteStream {

public static void main(String[] args) {
try {

FileInputStream fis = new FileInputStream("movie.mp4");
FileOutputStream fos = new FileOutputStream("movie_new.mp4");

byte input[] = new byte[50];
long before = System.currentTimeMillis();
int count = 0;
while (fis.read(input) != -1) {
fos.write(input);
count++;
}
fos.flush();
fis.close();
fos.close();
System.out.println(System.currentTimeMillis()-before+"ms");
System.out.println("done");

} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

}

4、使用带缓冲的字节流读写数据（字节流模板）

code：

package com.test;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class ReadByBufferedByteStream {

public static void main(String[] args) {
try {

FileInputStream fis = new FileInputStream("movie.mp4");
BufferedInputStream bis = new BufferedInputStream(fis,1000000);
FileOutputStream fos = new FileOutputStream("moive_new.mp4");
BufferedOutputStream bos = new BufferedOutputStream(fos,1000000);
//大型文件对应的数组可以大一些，小文件对应的数组小一些
byte input[] = new byte[100000];
int count = 0;
long before = System.currentTimeMillis();
while (bis.read(input) != -1) {
bos.write(input);
count++;
}
bos.flush();
bis.close();
fis.close();
bos.close();
fos.close();
System.out.println(System.currentTimeMillis()-before+"ms");
System.out.println("读取了："+count+"次");

} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

}

[b] 字符流：[/b]

1、使用字符流读写数据

code：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;

public class RWByCharStream {

public static void main(String[] args) {
try {

//File file = new File("java.txt");
FileInputStream fis = new FileInputStream("java.txt");
FileOutputStream fos = new FileOutputStream("java_new.txt");
InputStreamReader isr = new InputStreamReader(fis, "UTF-8");
OutputStreamWriter osw = new OutputStreamWriter(fos, "UTF-8");
char input[] = new char[100];
int l = 0;
while ((l = isr.read(input)) != -1) {
//String inputString = new String(input,0,l);
osw.write(input,0,l);
}
isr.close();
fis.close();
osw.close();
fos.close();
System.out.println("done");

} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

}

}

2、使用带有缓冲的字符流读写数据（字符流模板）

code：

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;

public class RWByBufferedCharStream {

public static void main(String[] args) {
try {

//File file = new File("java.txt");
FileInputStream fis = new FileInputStream("java.txt");
FileOutputStream fos = new FileOutputStream("java_new_buff.txt");
InputStreamReader isr = new InputStreamReader(fis, "UTF-8");
OutputStreamWriter osw = new OutputStreamWriter(fos, "UTF-8");

BufferedReader br = new BufferedReader(isr);
//BufferedWriter bw = new BufferedWriter(osw);
PrintWriter pw = new PrintWriter(osw,true);

String input;
while ((input = br.readLine()) != null) {
//bw.write(input);
pw.println(input);
}
br.close();
//bw.flush();bw.close();
pw.close();
isr.close();
fis.close();
osw.close();
fos.close();
System.out.println("done");

} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

}