1 public class FileUtils {  2     /**  3      * 遍历目录  遍历出目录下的文件名和子目录名  4      *  5      * @param dir 目录  6      * @throws IllegalAccessException  7      */  8     public static void listDirectory(File dir) throws IllegalAccessException {  9         if (!dir.exists()) { 10             throw new IllegalAccessException("目录：" + dir + "不存在"); 11         } 12         if (!dir.isDirectory()) { 13             throw new IllegalAccessException(dir + "不是目录"); 14         } 15         String[] fileNames = dir.list(); 16         for (String s : fileNames) { 17             System.out.println(dir + "//" + s); 18         } 19     } 20  21     /** 22      * 一个字节一个字节的复制文件 23      * 24      * @param srcFile 25      * @param destFile 26      * @throws IllegalAccessException 27      * @throws IOException 28      */ 29     public static void copyFileByByte(File srcFile, File destFile) throws IllegalAccessException, IOException { 30         if (!srcFile.exists()) { 31             throw new IllegalAccessException("文件:" + srcFile + "不存在"); 32         } 33         if (!srcFile.isFile()) { 34             throw new IllegalAccessException(srcFile + "不是文件"); 35         } 36         FileInputStream in = new FileInputStream(srcFile); 37         FileOutputStream out = new FileOutputStream(destFile); 38         int b; 39         while ((b = in.read()) != -1) { 40             out.write(b); 41             out.flush(); 42         } 43         in.close(); 44         out.close(); 45     } 46  47     /** 48      * 批量复制文件 49      * 50      * @param srcFile  源文件对象 51      * @param destFile 复制到的文件对象 52      * @throws IllegalAccessException 53      * @throws FileNotFoundException 54      */ 55     public static void copyFile(File srcFile, File destFile) throws IllegalAccessException, IOException { 56         if (!srcFile.exists()) { 57             throw new IllegalAccessException("文件:" + srcFile + "不存在"); 58         } 59         if (!srcFile.isFile()) { 60             throw new IllegalAccessException(srcFile + "不是文件"); 61         } 62         FileInputStream in = new FileInputStream(srcFile); 63         FileOutputStream out = new FileOutputStream(destFile); 64         byte[] buf = new byte[8 * 1024]; 65         int b; 66         while ((b = in.read(buf, 0, buf.length)) != -1) { 67             out.write(buf, 0, b); 68             out.flush(); 69         } 70         in.close(); 71         out.close(); 72     } 73  74     /** 75      * 复制文件 利用缓冲区 76      * 77      * @param srcFile 78      * @param destFile 79      * @throws IllegalAccessException 80      * @throws IOException 81      */ 82     public static void copyFileByBuffer(File srcFile, File destFile) throws IllegalAccessException, IOException { 83         if (!srcFile.exists()) { 84             throw new IllegalAccessException("文件:" + srcFile + "不存在"); 85         } 86         if (!srcFile.isFile()) { 87             throw new IllegalAccessException(srcFile + "不是文件"); 88         } 89         BufferedInputStream bis = new BufferedInputStream(new FileInputStream(srcFile)); 90         BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(destFile)); 91         int c = 0; 92         while ((c = bis.read()) != -1) { 93             bos.write(c); 94             //刷新缓存区 95             bos.flush(); 96         } 97         bis.close(); 98         bos.close(); 99     }100 101     /**102      * 批量缓存复制文件103      *104      * @param srcFile105      * @param destFile106      * @throws IllegalAccessException107      * @throws IOException108      */109     public static void copyFileBatchBuffer(File srcFile, File destFile) throws IllegalAccessException, IOException {110         if (!srcFile.exists()) {111             throw new IllegalAccessException("文件:" + srcFile + "不存在");112         }113         if (!srcFile.isFile()) {114             throw new IllegalAccessException(srcFile + "不是文件");115         }116         BufferedInputStream bis = new BufferedInputStream(new FileInputStream(srcFile));117         BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(destFile));118         byte[] buf = new byte[8 * 1024];119         int b;120         while ((b = bis.read(buf, 0, buf.length)) != -1) {121             bos.write(buf, 0, b);122             bos.flush();123         }124         bis.close();125         bos.close();126     }127 128     /**129      * 复制 1.76M MP4文件用时比较130      *131      * @param args132      * @throws IllegalAccessException133      * @throws IOException134      */135     public static void main(String[] args) throws IllegalAccessException, IOException {136         long startTime = System.currentTimeMillis();137         //单字节复制用时：6596ms138         copyFileByByte(new File("D:\\文件\\QQ视频20180718111001.mp4"), new File("D:\\文件\\1.mp4"));139         //批量复制：6ms140         copyFile(new File("D:\\文件\\QQ视频20180718111001.mp4"), new File("D:\\文件\\2.mp4"));141         //单字节缓存复制用时：2709ms142         copyFileByBuffer(new File("D:\\文件\\QQ视频20180718111001.mp4"), new File("D:\\文件\\3.mp4"));143         //批量缓存复制用时：5ms144         copyFileBatchBuffer(new File("D:\\文件\\QQ视频20180718111001.mp4"), new File("D:\\文件\\4.mp4"));145         long endTime = System.currentTimeMillis();146         System.out.println(endTime - startTime);147     }148 }