Java常用字节流和字符流实例汇总

package com.wxd.test2;

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

public class IOUtil {
  /**
   * 读取指定文件内容，按照16进制输出到控制台
   * 并且每输出10个byte换行
   * @param fileName
   */
  public static void printHex(String fileName) throws IOException {
    //把文件作为字节流进行读操作
    FileInputStream in =new FileInputStream(fileName);
    int b;
    int i=1;
    while ((b=in.read())!=-1){
      if(b<=0xf){
        //单位数前面补0
        System.out.print(0);
      }
      System.out.print(Integer.toHexString(b)+" ");
      if(i++%10==0){
        System.out.println();
      }
    }
    in.close();
  }
}

package com.wxd.test2;

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

public class FileOutDemo1 {
  public static void main(String[] args) throws IOException{
    //如果该文件不存在则直接创建，如果存在删除后创建
    FileOutputStream out=new FileOutputStream("demo/out.dat");
    out.write('A');//写出了‘A'字符的低八位
    out.write('B');//写出了‘B'字符的低八位
    int a=10;//write只能写低八位写一个int需要写四次每次8位
    out.write(a>>>24);
    out.write(a>>>16);
    out.write(a>>>8);
    out.write(a);
    byte[] zg="中国".getBytes("UTF-8");
    out.write(zg);
    out.close();

    IOUtil.printHex("demo/out.dat");

  }
}

package com.wxd.test2;

import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class DosDemo {
  public static void main(String[] args) throws IOException {
    String file="demo/dos.dat";
    DataOutputStream dos=new DataOutputStream(new FileOutputStream(file));
    dos.writeInt(10);
    dos.writeInt(-10);
    dos.writeLong(10l);
    dos.writeDouble(10.5);
    //采用UTF-8编码写出
    dos.writeUTF("中国");
    //采用utf-16be编码写出
    dos.writeChars("中国");
    dos.close();
  }
}

package com.wxd.test2;

import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class DisDemo {
  public static void main(String[] args) throws IOException {
    String file="demo/dos.dat";
    DataInputStream dis=new DataInputStream(new FileInputStream(file));
    int i=dis.readInt();//其实做了4次read,因为int是32位
    System.out.println(i);
     i=dis.readInt();
    System.out.println(i);
    long l=dis.readLong();//其实做了8次read，应为long是64位
    System.out.println(l);
    double d=dis.readDouble();
    System.out.println(d);
    String s=dis.readUTF();
    System.out.println(s);
    dis.close();
  }
}

/***
   *进行文件的拷贝，利用带缓冲的字节流
   * @param srcFile
   * @param destFile
   * @throws IOException
   */
  public static void copyFileByBuffer(File srcFile,File destFile) throws IOException{
    if(!srcFile.exists()){
      throw new IllegalArgumentException("文件："+srcFile+"不存在");
    }
    if(!srcFile.isFile()){
      throw new IllegalArgumentException(srcFile+"不是文件！");
    }
    BufferedInputStream bis=new BufferedInputStream(new FileInputStream(srcFile));
    BufferedOutputStream bos=new BufferedOutputStream(new FileOutputStream(destFile));
    int c;
    while ((c=bis.read())!=-1){
      bos.write(c);
      bos.flush();//刷新缓冲区，否则写入不到；
    }
    bis.close();
    bos.close();
  }

package com.wxd.test2;

import java.io.*;

public class IsrAndOswDemo {
  public static void main(String[] args) throws IOException{
    //InputStreamReader被称为桥梁流
    FileInputStream in=new FileInputStream("demo\\test.txt");//默认项目的编码，操作的时候要写文件本身的编码
    InputStreamReader isr=new InputStreamReader(in,"utf-8");
    FileOutputStream out=new FileOutputStream("demo\\test2.txt");
    OutputStreamWriter osw=new OutputStreamWriter(out,"utf-8");
//    int c;
//    while ((c=isr.read())!=-1){
//      System.out.print((char)c);
//    }
    char[] buffer=new char[8*1024];
    int c;
    //批量读取，放入buffer这个字符数组，从第0个位置开始放置，最多放buffe.length个
    //返回的是读到的字符的个数
    while ((c=isr.read(buffer,0,buffer.length))!=-1){
      String s=new String(buffer,0,c);
      System.out.println(s);
      osw.write(buffer,0,c);
      osw.flush();
    }
    isr.close();
    osw.close();
  }
}

package com.wxd.test2;

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

public class FrAndFwDemo {
  public static void main(String[] args) throws IOException{
    FileReader fr=new FileReader("demo\\test.txt");
    FileWriter fw=new FileWriter("demo\\text2.txt",true);//设置为true在后面追加
    char[] buffer=new char[2056];
    int c;
    while ((c=fr.read(buffer,0,buffer.length))!=-1){
      fw.write(buffer,0,c);
      fw.flush();
    }
    fr.close();
    fw.close();
  }
}

package com.wxd.test2;

import java.io.*;

public class BrAndBwOrPwDemo {
  public static void main(String[] args) throws IOException {
    //对文件进行读写操作
    BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream("demo\\test.txt")));
    /*BufferedWriter bw=new BufferedWriter(new OutputStreamWriter(new FileOutputStream("demo\\test3.txt")));*/
    PrintWriter pw = new PrintWriter("demo\\test3.txt");
    String line;
    while ((line = br.readLine()) != null) {
      System.out.println(line);//一次读一行，并不能识别换行
      /*bw.write(line);
      //单独写出换行操作
      bw.newLine();
      bw.flush();*/
      pw.println(line);
      pw.flush();
    }
    br.close();
//    bw.close();
    pw.close();
  }
}