文件读取、复制

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package io1;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0System.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();}}
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