字符流..

 字符输入流

package MONA.demo02_字符输入流;

import java.io.FileReader;

public class Demo {
    public static void main(String[] args) throws Exception {
        FileReader fr = new FileReader("2.txt");
        //20320
        //System.out.println((char)fr.read());

        //单个读取
        int i = 0;
        while ((i = fr.read()) != -1){
            System.out.println((char)i);
        }

        //读取到数组里面
        char[] chars = new char[3];
        int count = 0;
        while ((count = fr.read(chars)) !=-1){
            for (int j = 0; j < chars.length; j++) {
                System.out.println(chars[j]);
            }
        }
    }
}

字符输出流

package MONA.demo03_字符输出流;

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

public class Demo {
    public static void main(String[] args) throws IOException {
        FileWriter fw = new FileWriter("3.txt");
        fw.write("你好呀");
        //刷新
        fw.flush();

        char[] chars = {'美','女'};
        fw.write(chars);
        //fw.flush();
        //关闭流：关闭后会自动刷新
        fw.close();
    }
}

使用字符流复制文本文件 

package MONA.demo04_练习题;
import java.io.FileReader;
import java.io.FileWriter;
public class Demo01 {
    public static void main(String[] args) throws Exception {
        //边读取边输出
        FileReader fr = new FileReader("test.txt");
        FileWriter fw = new FileWriter("testCopy.txt");

        int c = 0;
        while ((c = fr.read()) !=-1){
            fw.write(c);
            //刷新
            fw.flush();
        }
        fw.close();
        fr.close();
        System.out.println("复制完毕");
    }
}

字节流转换为字符流

FileOutputStream：将一个字节输出流转换成字符输出流，方便字节写入字符

package MONA.demo05_转换流;

import java.io.FileOutputStream;
import java.io.OutputStreamWriter;


public class Demo {
    public static void main(String[] args) throws Exception {
        //将一个字节输出流转换成字符输出流，方便字节写入字符
        FileOutputStream fos = new FileOutputStream("4.txt");
        //转换流
        OutputStreamWriter osw = new OutputStreamWriter(fos);
        osw.write("你好");
        osw.close();
        fos.close();
        System.out.println("转换完成");
    }
}

InputStreamReader：将一个字节输入流包装成字符输入流，方便读取字符

package MONA.demo05_转换流;

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

public class Demo {
    public static void main(String[] args) throws IOException {
        FileInputStream fis = new FileInputStream("1.txt");
        //转换
        InputStreamReader isr = new InputStreamReader(fis);
        int c = isr.read();
        System.out.println((char)c);
    }
}

 结构整理

字节输入流
    InputStream
        FileInputStream
字节输出流 
    OutputStream 
        FileOutputStream 
字符输入流
     Reader
        InputStreamReader(转换流)
            FileReader
 字符输出流
      Writer
        OutputStreamWriter(转换流)
            FileWriter

package MONA.demo07_字符编码;


import java.io.FileInputStream;
import java.util.TreeMap;


public class Demo01 {
    public static void main(String[] args) throws Exception {
//        FileInputStream fis = new FileInputStream("2.txt");
//        //将所有的内容都读取到，之后再遍历
//        byte[] bytes = new byte[10];
//        int count = 0;
//        StringBuffer sb = new StringBuffer();
//        while ((count = fis.read(bytes)) !=-1){
//            sb.append(new String (bytes,0,count));
//        }
//        TreeMap treeMap = new TreeMap<>();
//        for(char c :sb.toString().toCharArray()) {
//            //进行统计
//            //containsKey 是否包含指定的key
//            treeMap.put(c, treeMap.containsKey(c) ? treeMap.get(c) + 1 : 1);
//        }
//        System.out.println(treeMap);

        TreeMap treeMap = new TreeMap<>();
        //边读取边统计
        FileInputStream fis = new FileInputStream("2.txt");
        int n = 0;
        while((n = fis.read()) != -1){
            char c = (char) n;
            treeMap.put(c, treeMap.containsKey(c) ? treeMap.get(c) + 1 : 1);
        }
        System.out.println(treeMap);
    }
}