IO操作工具类

Posted 2020-08-21 霓裳梦竹

package com.imooc.io;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
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
     * 单字节读取不适合大文件，大文件效率很低
     */
    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();
    }
    /**
     * 批量读取，对大文件而言效率高，也是我们最常用的读文件的方式
     * @param fileName
     * @throws IOException
     */
    public static void printHexByByteArray(String fileName)throws IOException{
        FileInputStream in = new FileInputStream(fileName);
        byte[] buf = new byte[8 * 1024];
        /*从in中批量读取字节，放入到buf这个字节数组中，
         * 从第0个位置开始放，最多放buf.length个 
         * 返回的是读到的字节的个数
        */
        /*int bytes = in.read(buf,0,buf.length);//一次性读完，说明字节数组足够大
        int j = 1; 
        for(int i = 0; i < bytes;i++){
            System.out.print(Integer.toHexString(buf[i] & 0xff)+"  ");
            if(j++%10==0){
                System.out.println();
            }
        }*/
      int bytes = 0;
      int j = 1;
      while((bytes = in.read(buf,0,buf.length))!=-1){
          for(int i = 0 ; i < bytes;i++){
              System.out.print(Integer.toHexString(buf[i] & 0xff)+"  ");
              if(j++%10==0){
                  System.out.println();
              }
          }
      }
      in.close();
    }
    /**
     * 文件拷贝，字节批量读取
     * @param srcFile
     * @param destFile
     * @throws IOException
     */
    public static void copyFile(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");
        }
        FileInputStream in = new FileInputStream(srcFile);
        FileOutputStream out = new FileOutputStream(destFile);
        byte[] buf = new byte[8*1024];
        int b ;
        while((b = in.read(buf,0,buf.length))!=-1){
            out.write(buf,0,b);
            out.flush();//最好加上
        }
        in.close();
        out.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
        }
        bis.close();
        bos.close();
    }
    /**
     * 单字节，不带缓冲进行文件拷贝
     * @param srcFile
     * @param destFile
     * @throws IOException
     */
    public static void copyFileByByte(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");
        }
        FileInputStream in = new FileInputStream(srcFile);
        FileOutputStream out = new FileOutputStream(destFile);
        int c ;
        while((c = in.read())!=-1){
            out.write(c);
            out.flush();
        }
        in.close();
        out.close();
    }
    
}