字节流

  1 import java.io.BufferedInputStream;
  2 import java.io.BufferedOutputStream;
  3 import java.io.File;
  4 import java.io.FileInputStream;
  5 import java.io.FileOutputStream;
  6 import java.io.IOException;
  7 
  8 public class IOUtil {
  9     /**
 10      * 读取指定文件内容，按照16进制输出到控制台
 11      * 并且每输出10个byte换行
 12      * @param fileName
 13      * 单字节读取不适合大文件，大文件效率很低
 14      */
 15     public static void printHex(String fileName)throws IOException{
 16         //把文件作为字节流进行读操作
 17         FileInputStream in = new FileInputStream(fileName);
 18         int b ;
 19         int i = 1;
 20         while((b = in.read())!=-1){
 21             if(b <= 0xf){
 22                 //单位数前面补0
 23                 System.out.print("0");
 24             }
 25             System.out.print(Integer.toHexString(b)+"  ");
 26             if(i++%10==0){
 27                 System.out.println();
 28             }
 29         }
 30         in.close();
 31     }
 32     /**
 33      * 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
 34      * @param fileName
 35      * @throws IOException
 36      */
 37     public static void printHexByByteArray(String fileName)throws IOException{
 38         FileInputStream in = new FileInputStream(fileName);
 39         byte[] buf = new byte[8 * 1024];
 40         /*从in中批量读取字节，放入到buf这个字节数组中，
 41          * 从第0个位置开始放，最多放buf.length个 
 42          * 返回的是读到的字节的个数
 43         */
 44         /*int bytes = in.read(buf,0,buf.length);//一次性读完，说明字节数组足够大
 45         int j = 1; 
 46         for(int i = 0; i < bytes;i++){
 47             System.out.print(Integer.toHexString(buf[i] & 0xff)+"  ");
 48             if(j++%10==0){
 49                 System.out.println();
 50             }
 51         }*/
 52       int bytes = 0;
 53       int j = 1;
 54       while((bytes = in.read(buf,0,buf.length))!=-1){
 55           for(int i = 0 ; i < bytes;i++){
 56               System.out.print(Integer.toHexString(buf[i] & 0xff)+"  ");
 57               if(j++%10==0){
 58                   System.out.println();
 59               }
 60           }
 61       }
 62       in.close();
 63     }
 64     /**
 65      * 文件拷贝，字节批量读取
 66      * @param srcFile
 67      * @param destFile
 68      * @throws IOException
 69      */
 70     public static void copyFile(File srcFile,File destFile)throws IOException{
 71         if(!srcFile.exists()){
 72             throw new IllegalArgumentException("文件:"+srcFile+"不存在");
 73         }
 74         if(!srcFile.isFile()){
 75             throw new IllegalArgumentException(srcFile+"不是文件");
 76         }
 77         FileInputStream in = new FileInputStream(srcFile);
 78         FileOutputStream out = new FileOutputStream(destFile);
 79         byte[] buf = new byte[8*1024];
 80         int b ;
 81         while((b = in.read(buf,0,buf.length))!=-1){
 82             out.write(buf,0,b);
 83             out.flush();//最好加上
 84         }
 85         in.close();
 86         out.close();
 87         
 88     }
 89     /**
 90      * 进行文件的拷贝，利用带缓冲的字节流
 91      * @param srcFile
 92      * @param destFile
 93      * @throws IOException
 94      */
 95     public static void copyFileByBuffer(File srcFile,File destFile)throws IOException{
 96         if(!srcFile.exists()){
 97             throw new IllegalArgumentException("文件:"+srcFile+"不存在");
 98         }
 99         if(!srcFile.isFile()){
100             throw new IllegalArgumentException(srcFile+"不是文件");
101         }
102         BufferedInputStream bis = new BufferedInputStream(
103                 new FileInputStream(srcFile));
104         BufferedOutputStream bos = new BufferedOutputStream(
105                 new FileOutputStream(destFile));
106         int c ;
107         while((c = bis.read())!=-1){
108             bos.write(c);
109             bos.flush();//刷新缓冲区
110         }
111         bis.close();
112         bos.close();
113     }
114     /**
115      * 单字节，不带缓冲进行文件拷贝
116      * @param srcFile
117      * @param destFile
118      * @throws IOException
119      */
120     public static void copyFileByByte(File srcFile,File destFile)throws IOException{
121         if(!srcFile.exists()){
122             throw new IllegalArgumentException("文件:"+srcFile+"不存在");
123         }
124         if(!srcFile.isFile()){
125             throw new IllegalArgumentException(srcFile+"不是文件");
126         }
127         FileInputStream in = new FileInputStream(srcFile);
128         FileOutputStream out = new FileOutputStream(destFile);
129         int c ;
130         while((c = in.read())!=-1){
131             out.write(c);
132             out.flush();
133         }
134         in.close();
135         out.close();
136     }
137     
138 }