I/O Streams -1Byte Streams，Character Streams

流	父类	子类
Byte Streams	InputStream OutputStream	FileInputStream FileOutputStream
Character Streams	Reader Writer	FileReader FileWriter

一般来说呢，不使用byte Streams，其他的流呢都是建立在byte Streams的基础上的。

Byte Streams(FileInputStream/FileOutputStream)

package tutorials;

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

public class CopyBytes {
    public static void main(String[] args) throws IOException{
        FileInputStream in = null;
        FileOutputStream out = null;
        
        try{
            in = new FileInputStream("D:/Learn/tutorials/src/xanadu.txt");
            out = new FileOutputStream("outagain.txt");
            int c;
            
            while((c=in.read()) != -1){
                //read方法返回的是int类型，这个int值是ASCII ，
                //如果读到文件的末尾，那么返回的是-1
                System.out.println(c);
                out.write(c);
            }
        } finally{
            if(in != null){
                in.close();
            }
            if(out != null){
                out.close();
            }
        }
    }
}

Character Streams(FileReader /FileWriter )

package tutorials;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class CopyCharacters {
    public static void main(String[] args) throws IOException{
        FileReader inputStream = null;
        FileWriter outputStream = null;
        
        try{
            inputStream = new FileReader("hah.txt");
            outputStream = new FileWriter("nihao.txt");
            int c;
            
            if((c=inputStream.read()) != -1){
                outputStream.write(c);
            }
        }finally{
            if(inputStream != null){
                inputStream.close();
            }
            if(outputStream != null){
                outputStream.close();
            }
        }
    }
}

上面两段程序唯一不同的地方就是将FileInputStream换成FileReader，FileOutputStream换成FileWriter
还有个区别就是程序中有个int c ，如果使用FileReader保存的是character value的后16位，FileInputStream保存的是character value的后8位。

line-oriented I/O

package tutorials;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;

public class CopyLines {
    public static void main(String[] args) throws IOException{
        BufferedReader inputStream = null;
        PrintWriter outputStream = null;
        
        try{
            inputStream = new BufferedReader(new FileReader("D:/Learn/tutorials/src/hah.txt"));
            outputStream = new PrintWriter(new FileWriter("nihao.txt"));
            //BufferedReader里面放的是Reader,PrintWriter里面放的是Writer，Reader和Writer都是Character Streams
            
            String l;
            while((l = inputStream.readLine()) != null){
                //BufferedReader.readLine方法，如果我们有值返回就返回String，如果没有值了就返回null
                //readline会一行一行的读取内容，识别的机制是读取到换行符（/n）或者回车键(/r)或者（/r/n）,能够适应各种操作系统
                outputStream.println(l);
                //printWriter.println方法，这个方法就是把把String中的内容写到PrintWriter中,然后加上换行符号
            }
        }finally{
            if(inputStream != null){
                inputStream.close();
            }
            if(outputStream != null){
                outputStream.close();
            }
        }
    }
}