java基础11（IO流）-字符流

转换流

由于字节流操作中文不是特别方便，所以java中提供了转换流

编码表：由现实世界的字符和对应的数值组成的一张表

编码：把看得懂的变成看不懂的(String-------byte[])

解码：把看不懂的变成看得懂的(byte[]-------String)

• String-----bytes[]

import java.util.Arrays;

import java.io.UnsupportedEncodingException;

public class StringDemo{

    public static void main(String[] args)throws UnsupportedEncodingException{

        String s = "你好";

        

        //String-----bytes[]

/*

        byte[] bys = s.getBytes();//将字符串转换成字节数组

        System.out.println(Arrays.toString(bys));//输出结果：[-28, -67, -96, -27, -91, -67]

*/



/*

        byte[] bys = s.getBytes("GBK");//指定编码方式

        System.out.println(Arrays.toString(bys));//输出结果：[-60, -29, -70, -61]        

*/



        byte[] bys = s.getBytes("utf-8");

        System.out.println(Arrays.toString(bys));//输出结果：[-28, -67, -96, -27, -91, -67]





    

    }

}

• bytes[]-----String

import java.io.UnsupportedEncodingException;

public class StringDemo{

    public static void main(String[] args)throws UnsupportedEncodingException{

        String s = "你好";

        

    //  byte[] bys = s.getBytes();//默认是utf-8编码

        byte[] bys = s.getBytes("utf-8");



        //byte[] ---Sttring

//      String ss = new String(bys);//utf-8编码的，utf-8解码的

//      System.out.println(ss);//转换成字符串;输出结果是你好

    

        String ss = new String(bys,"GBK");//utf-8编的,GBK解码的

        System.out.println(ss);//输出结果是：浣犲ソ

            

    }

}

OutputStreamWriter

OutputStreamWriter(OutputStream out) :使用默认编码把字节流的数据转换为字符流

OutputStreamWriter(OutputStream out, String charseName)：根据指定编码把字节流数据转换成字符流

OutputStreamWriter(或FileWriter)写数据

public void write(int c):写一个字符

public void write(char[] cbuf):写一个字符数组

public void write(char[] cbuf,int off,int len):写一个字符数组的一部分

public void write(String str):写一个字符串

public void write(String str,int off,int len):写一个字符串的一部分

代码练习

import java.io.FileOutputStream;

import java.io.OutputStreamWriter;

import java.io.IOException;



public class OutputStreamWriteDemo{

    public static void main(String[] args)throws IOException{

        //创建对象

        OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("/home/hadoop/a.txt"));



/*

        //写数据

        //public void write(int c):写一个字符

        osw.write("\na\n");

        osw.write(87);



*/



        //public void write(char[] cbuf):写一个字符数组

        char[] chs = {'a','b','c','d'};//不能使用双引号？

//      osw.write(chs);



        //public void write(char[] cbuf,int off,int len):写一个字符数组的一部分

//      osw.write(chs,1,3);





        //public void write(String str):

//      osw.write("自学java");

        

        //public void write(String str,int off, int len):写一个字符串的一部分

        osw.write("邬家栋自学java",3,6);

    

        osw.flush();

        osw.close();

        

    }

}

InputStreamReader

InputStreamReader(InputStream in) :用默认的编码读取数据

InputStreamReader(InputStream in, String charsetName) :用指定的编码读取数据

InputStreamReader(或FileReader)读取数据

int read():一次读取一个字符

int read(char[] chs):一次读取一个字符数组

代码练习

import java.io.FileInputStream;

import java.io.InputStreamReader;

import java.io.IOException;



public class InputStreamReadDemo{

    public static void main(String[] args)throws IOException{

        //创建对象

        InputStreamReader isr = new InputStreamReader(new FileInputStream("/home/hadoop/javatest/IO/OutputStreamWriteDemo.java"));



/*

        int ch = 0;

        while((ch = isr.read())!= -1){

            System.out.print((char)ch);

        }



*/



        //一次读取一个字符数组

        char[] chs = new char[1024];

        int len = 0;

        while((len = isr.read(chs)) != -1){

            System.out.print(new String(chs,0,len));

        }

    



        isr.close();

        

    }

}

字符流读写数据（复制文本文件）

import java.io.InputStreamReader;

import java.io.OutputStreamWriter;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;



public class CopyFileDemo{

    public static void main(String[] args)throws IOException{

        //封装数据源

        InputStreamReader isr = new InputStreamReader(new FileInputStream("/home/hadoop/a.txt"));

        //封装目的地

        OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("/home/hadoop/b.txt"));

        

/*

        //方式一

        int ch = 0;

        while((ch = isr.read()) != -1){

            osw.write(ch);

        }

*/



        //方式二

        char[] chs = new char[1024];

        int len = 0;

        while((len = isr.read(chs)) != -1){

            osw.write(chs,0,len);

            osw.flush();

    

        }



        isr.close();

        osw.close();

        

    }

}

字符缓冲流BufferedWriter写数据

import java.io.BufferedWriter;

import java.io.FileWriter;

import java.io.IOException;

import java.io.FileOutputStream;

import java.io.OutputStreamWriter;



public class BufferedWriterDemo{

    public static void main(String[] args)throws IOException{

        

        //BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("bw.txt")));

        BufferedWriter bw = new BufferedWriter(new FileWriter("bw.txt"));

        

        bw.write("hello\n");

        bw.write("wujiadong\n");



        bw.close();



    }

}

字符缓冲流BufferedReader读数据

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;



public class BufferedReaderDemo{

    public static void main(String[] args)throws IOException{

        //创建字符缓冲输入流对象

        BufferedReader br = new BufferedReader(new FileReader("bw.txt"));



/*

        //方式1

        int ch = 0;

        while((ch = br.read()) != -1){

            System.out.print((char) ch);

        }

*/



        //方式2

        char[] chs = new char[1024];

        int len = 0;

        while((len = br.read(chs)) != -1){

            System.out.print(new String(chs,0,len));

        }



        br.close();

    }

}

字符缓存流复制文件

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;



public class CopyFileDemo{

    public static void main(String[] args)throws IOException{

        //

        BufferedReader br = new BufferedReader(new FileReader("a.txt"));

        

        BufferedWriter bw = new BufferedWriter(new FileWriter("b.txt"));



        //方式1

        //方式2

        char[] chs = new char[1024];

        int len = 0;

        while((len = br.read(chs)) != -1){

            bw.write(chs,0,len);

            

        }



        br.close();

        bw.close();

    }

}

特殊功能（一次读一行）

• readLine(): 无换行符
• newline(): 换行

import java.io.BufferedWriter;

import java.io.FileWriter;

import java.io.IOException;

import java.io.BufferedReader;

import java.io.FileReader;



public class BufferedDemo{

    public static void main(String[] args)throws IOException{

    //  write();

        read();

    }



    public static void read()throws IOException{

        BufferedReader br = new BufferedReader(new FileReader("bw2.txt"));

        

        String line = null;

        while((line = br.readLine()) != null){

            System.out.println(line);

        }

        

        br.close();

        

    }

    

    public static void write() throws IOException{

        BufferedWriter bw = new BufferedWriter (new FileWriter("bw2.txt"));



        for(int i=0;i<10;i++){

            bw.write("wujiadong");

            bw.newLine(); //换行

            bw.flush();

        }



        bw.close();

    }



}

复制文件

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.IOException;

import java.io.FileReader;

import java.io.FileWriter;



public class CopyFileDemo1{

    public static void main(String[] args)throws IOException{

        //封装数据源

        BufferedReader br = new BufferedReader(new FileReader("CopyFileDemo.java"));



        //封装目的地

        BufferedWriter bw = new BufferedWriter(new FileWriter("bw3.txt"));



        String line = null;

        while((line = br.readLine()) != null){

            bw.write(line);

            bw.newLine();

            bw.flush();

        }



        br.close();

        bw.close();

    }

}

练习1：复制文本文件

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;



import java.io.BufferedReader;

import java.io.BufferedWriter;



public class CopyFileDemo{

    public static void main(String[] args)throws IOException{

        String srcString = "bw3.txt";

        String desString = "wu.txt";



//      method1(srcString,desString);

//      method2(srcString,desString);

//      method3(srcString,desString);

//      method4(srcString,desString);

        method5(srcString,desString);

        

    }



    //字符缓存流一次读写一个字符串

    private static void method5(String srcString,String desString)throws IOException{

        BufferedReader br = new BufferedReader(new FileReader(srcString));

        BufferedWriter bw = new BufferedWriter(new FileWriter(desString));



        String line = null;

        while((line = br.readLine()) != null){

            bw.write(line);

            bw.newLine();

            bw.flush();

        }



        br.close();

        bw.close();

    }

    



    //字符缓存流一次读写一个字符数组

    private static void method4(String srcString,String desString)throws IOException{

        BufferedReader br = new BufferedReader(new FileReader(srcString));

        BufferedWriter bw = new BufferedWriter(new FileWriter(desString));

    

        char[] ch = new char[1024];

        int len = 0;

        while((len = br.read(ch)) != -1){

            bw.write(ch);

        }



        br.close();

        bw.close();

    }



    //字符缓冲流一次读写一个字符

    private static void method3(String srcString,String desString)throws IOException{

        BufferedReader fr = new BufferedReader(new FileReader(srcString));

        BufferedWriter fw = new BufferedWriter(new FileWriter(desString));



        int ch = 0;

        while((ch = fr.read()) != -1){

            fw.write(ch);

        }       

        

        fr.close();

        fw.close();

            

    }



    //基本字符流一次读取一个字符数组

    private static void method2(String srcString,String desString)throws IOException{

        FileReader fr = new FileReader(srcString);

        FileWriter fw = new FileWriter(desString);

        

        char[] ch = new char[1024];

        int len = 0;

        while((len = fr.read(ch)) != -1){

            fw.write(ch, 0 ,len);

        }

        

        fr.close();

        fw.close();

    }



    //基本字符流一次读写一个字符

    private static void method1(String srcString,String desString)throws IOException{

        FileReader fr = new FileReader(srcString);

        FileWriter fw = new FileWriter(desString);



        int ch = 0;

        while((ch = fr.read()) != -1){

            fw.write(ch);

        }



        fr.close();

        fw.close();

    }

}

练习2：复制非文本文件的4种方法

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;



import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;



public class CopyImageDemo{

    public static void main(String[] args)throws IOException{

        //使用字符串作为路径

//      String srcFile = "1.jpg";

//      String desFile = "/home/hadoop/javatest/1.jpg";

        

        //使用File对象作为参数

        File srcFile = new File("/home/hadoop/1.jpg");

        File desFile = new File("/home/hadoop/javatest/1.jpg");



//      method1(srcFile,desFile);

//      method2(srcFile,desFile);

//      method3(srcFile,desFile);

        method4(srcFile,desFile);

    }



    //基本字节流一次读取一个字节

    public static void method1(File srcFile,File desFile)throws IOException{

        FileInputStream fis = new FileInputStream(srcFile);

        FileOutputStream fos = new FileOutputStream(desFile);



        int by = 0;

        while((by = fis.read()) != -1){

            fos.write(by);

        }



        fis.close();

        fos.close();

    }



    //基本字节流一次读写一个字节数组

    public static void method2(File srcFile,File desFile)throws IOException{

        FileInputStream fis = new FileInputStream(srcFile);

        FileOutputStream fos = new FileOutputStream(desFile);

        

        byte[] by = new byte[1024];

        int len = 0;

        while((len = fis.read(by)) != -1){

            fos.write(len);

            fos.flush();

        }



        fis.close();

        fos.close();



    }   



    public static void method3(File srcFile,File desFile)throws IOException{

        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(srcFile));

        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(desFile));



        int by = 0;

        while((by = bis.read()) != -1){

            bos.write(by);

        }



        bis.close();

        bos.close();

    }



    //字节缓冲流一次读取一个字节数组

    public static void method4(File srcFile,File desFile)throws IOException{

        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(srcFile));

        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(desFile));



        byte[] by = new byte[1024];

        int len = 0;

        while((len = bis.read()) != -1){

            bos.write(by);

            bos.flush();

        }

    

        bis.close();

        bos.close();



    }

    

}

练习3：将集合中的数据存储到文本文件

/*

 * 需求：将ArrayList集合中的字符串数据存储到文本文件

 *

 */

import java.util.ArrayList;

import java.io.BufferedWriter;

import java.io.IOException;

import java.io.FileWriter;



public class ArrayListToFileDemo{

    public static void main(String[] args)throws IOException{

        //创建集合对象

        ArrayList<String> array = new ArrayList<String>();



        array.add("java");

        array.add("python");

        array.add("scala");



        //封装目的地

        BufferedWriter bw = new BufferedWriter(new FileWriter("/home/hadoop/wu.txt"));  



        //遍历集合

        for(String s:array){

            bw.write(s);

            bw.newLine();

        }



        bw.close();

    }

}

练习4：把文本文件的数据存储到集合

/*

 * 需求：从文本文件中读取数据（一行为一个字符串数据）到集合中,并遍历集合

 *

 *

 */

import java.util.ArrayList;

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;



public class FileToArrayListDemo{

    public static void main(String[] args)throws IOException{

        //封装数据源

        BufferedReader br = new BufferedReader(new FileReader("/home/hadoop/wu.txt"));



        //封装目的地

        ArrayList<String> array = new ArrayList<String>();



        //读取数据存储到集合中

        String line = null;

        while((line = br.readLine()) != null){

            array.add(line);

        }



        br.close();



        //遍历集合

        for(String s:array){

            System.out.println(s);

        }

    }

}

练习5：

/*

 * 需求：有一个文本文件存储了几个名称，写一个程序实现随机获取一个人的名字

 *

 */

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

import java.util.ArrayList;

import java.util.Random;



public class GetName{

    public static void main(String[] args)throws IOException{

        //把文本文件的数据存储到集合中

        BufferedReader br = new BufferedReader(new FileReader("/home/hadoop/wu.txt"));

        ArrayList<String> array = new ArrayList<String>();

        

        String line = null;

        while((line = br.readLine()) != null){

            array.add(line);

        }



        br.close();

    

        //产生一个随机索引

        Random r = new Random();

        int index = r.nextInt(array.size());

        

        //根据该索引获取一个值

        String name = array.get(index);

        System.out.println("幸运者是："+name);



    }

}

练习6：复制单级文件夹

import java.io.File;



import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.IOException;

import java.io.FileInputStream;

import java.io.FileOutputStream;



public class CopyFolderDemo{

    public static void main(String[] args)throws IOException{

        //封装目录

        File srcFolder = new File("/home/hadoop/javatest/IO");

        File desFolder = new File("/home/hadoop/wu_test");



        //如果目的地文件夹不存在就创建

        if(!desFolder.exists()){

            desFolder.mkdir();

        }



        //获取该目录下的所有文本的File数组

        File[] fileArray = srcFolder.listFiles();



        //遍历该File数组，得到么一个File对象

        for(File file:fileArray){

            //System.out.println(file);

            //数据源：/home/hadoop/javatest

            //目的地：/home/hadoop/wu_test



            String name = file.getName();

            File newFile = new File(desFolder,name);



            copyFile(file,newFile);

        }

    }



    private static void copyFile(File file,File newFile)throws IOException{

        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file));

        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(newFile));



        byte[] by = new byte[1024];

        int len = 0;

        while((len = bis.read(by)) != -1){

            bos.write(by,0,len);

        }



        bos.close();

        bis.close();

        

    }