基于Java回顾之I/O的使用详解

使用FileInputStream读取文件信息 public static byte[] readFileByFileInputStream(File file) throws IOException {     ByteArrayOutputStream output = new ByteArrayOutputStream();     FileInputStream fis = null;     try     {         fis = new FileInputStream(file);         byte[] buffer = new byte[1024];         int bytesRead = 0;         while((bytesRead = fis.read(buffer, 0, buffer.length)) != -1)         {             output.write(buffer, 0, bytesRead);         }     }     catch(Exception ex)     {         System.out.println("Error occurs during reading " + file.getAbsoluteFile());     }     finally     {         if (fis !=null) fis.close();         if (output !=null) output.close();     }     return output.toByteArray(); }

 public static byte[] readFileByBufferedInputStream(File file) throws Exception {     FileInputStream fis = null;     BufferedInputStream bis = null;     ByteArrayOutputStream output = new ByteArrayOutputStream();     try     {         fis = new FileInputStream(file);         bis = new BufferedInputStream(fis);         byte[] buffer = new byte[1024];         int bytesRead = 0;         while((bytesRead = bis.read(buffer, 0, buffer.length)) != -1)         {             output.write(buffer, 0, bytesRead);         }     }     catch(Exception ex)     {         System.out.println("Error occurs during reading " + file.getAbsoluteFile());     }     finally     {         if (fis != null) fis.close();         if (bis != null) bis.close();         if (output != null) output.close();     }     return output.toByteArray(); }

使用FileOutputStream复制文件 public static void copyFileByFileOutputStream(File file) throws IOException {     FileInputStream fis = null;     FileOutputStream fos = null;     try     {         fis = new FileInputStream(file);         fos = new FileOutputStream(file.getName() + ".bak");         byte[] buffer = new byte[1024];         int bytesRead = 0;         while((bytesRead = fis.read(buffer,0,buffer.length)) != -1)         {             fos.write(buffer, 0, bytesRead);         }         fos.flush();     }     catch(Exception ex)     {         System.out.println("Error occurs during copying " + file.getAbsoluteFile());     }     finally     {         if (fis != null) fis.close();         if (fos != null) fos.close();     } }

使用BufferedOutputStream复制文件 public static void copyFilebyBufferedOutputStream(File file)throws IOException {     FileInputStream fis = null;     BufferedInputStream bis = null;     FileOutputStream fos = null;     BufferedOutputStream bos = null;     try     {         fis = new FileInputStream(file);         bis = new BufferedInputStream(fis);         fos = new FileOutputStream(file.getName() + ".bak");         bos = new BufferedOutputStream(fos);         byte[] buffer = new byte[1024];         int bytesRead = 0;         while((bytesRead = bis.read(buffer, 0, buffer.length)) != -1)         {             bos.write(buffer, 0, bytesRead);         }         bos.flush();     }     catch(Exception ex)     {         System.out.println("Error occurs during copying " + file.getAbsoluteFile());     }     finally     {         if (fis != null) fis.close();         if (bis != null) bis.close();         if (fos != null) fos.close();         if (bos != null) bos.close();     } }

使用BufferedReader读取文件内容 public static String readFile(String file)throws IOException {     BufferedReader br = null;     StringBuffer sb = new StringBuffer();     try     {         br = new BufferedReader(new FileReader(file));         String line = null;         while((line = br.readLine()) != null)         {             sb.append(line);         }     }     catch(Exception ex)     {         System.out.println("Error occurs during reading " + file);     }     finally     {         if (br != null) br.close();     }     return sb.toString(); }

使用BufferedWriter复制文件 public static void copyFile(String file) throws IOException {      BufferedReader br = null;     BufferedWriter bw = null;     try     {         br = new BufferedReader(new FileReader(file));         bw = new BufferedWriter(new FileWriter(file + ".bak"));         String line = null;         while((line = br.readLine())!= null)         {             bw.write(line);         }     }     catch(Exception ex)     {         System.out.println("Error occurs during copying " + file);     }     finally     {         if (br != null) br.close();         if (bw != null) bw.close();     } }

创建大小固定的文件 public static void createFile(String file, int size) throws IOException {     File temp = new File(file);     RandomAccessFile raf = new RandomAccessFile(temp, "rw");     raf.setLength(size);     raf.close(); }

向文件中随机插入数据 public static void writeFile(String file, byte[] content, int startPos, int contentLength) throws IOException {     RandomAccessFile raf = new RandomAccessFile(new File(file), "rw");     raf.seek(startPos);     raf.write(content, 0, contentLength);     raf.close(); }

移动文件 public static boolean moveFile(String sourceFile, String destFile) {     File source = new File(sourceFile);     if (!source.exists()) throw new RuntimeException("source file does not exist.");     File dest = new File(destFile);     if (!(new File(dest.getPath()).exists())) new File(dest.getParent()).mkdirs();     return source.renameTo(dest); }

复制文件 public static void copyFile(String sourceFile, String destFile) throws IOException {     File source = new File(sourceFile);     if (!source.exists()) throw new RuntimeException("File does not exist.");     if (!source.isFile()) throw new RuntimeException("It is not file.");     if (!source.canRead()) throw new RuntimeException("File cound not be read.");     File dest = new File(destFile);     if (dest.exists())     {         if (dest.isDirectory()) throw new RuntimeException("Destination is a folder.");         else         {             dest.delete();         }     }     else     {         File parentFolder = new File(dest.getParent());         if (!parentFolder.exists()) parentFolder.mkdirs();         if (!parentFolder.canWrite()) throw new RuntimeException("Destination can not be written.");     }     FileInputStream fis = null;     FileOutputStream fos = null;     try     {         fis = new FileInputStream(source);         fos = new FileOutputStream(dest);         byte[] buffer = new byte[1024];         int bytesRead = 0;         while((bytesRead = fis.read(buffer, 0, buffer.length)) != -1)         {             fos.write(buffer, 0, bytesRead);         }         fos.flush();     }     catch(IOException ex)     {         System.out.println("Error occurs during copying " + sourceFile);     }     finally     {         if (fis != null) fis.close();         if (fos != null) fos.close();     } }

复制文件夹 public static void copyDir(String sourceDir, String destDir) throws IOException {     File source = new File(sourceDir);     if (!source.exists()) throw new RuntimeException("Source does not exist.");     if (!source.canRead()) throw new RuntimeException("Source could not be read.");     File dest = new File(destDir);     if (!dest.exists()) dest.mkdirs();     File[] arrFiles = source.listFiles();     for(int i = 0; i < arrFiles.length; i++)     {         if (arrFiles[i].isFile())         {             BufferedReader reader = new BufferedReader(new FileReader(arrFiles[i]));             BufferedWriter writer = new BufferedWriter(new FileWriter(destDir + "/" + arrFiles[i].getName()));             String line = null;             while((line = reader.readLine()) != null) writer.write(line);             writer.flush();             reader.close();             writer.close();         }         else         {             copyDir(sourceDir + "/" + arrFiles[i].getName(), destDir + "/" + arrFiles[i].getName());         }     } }

删除文件夹 public static void del(String filePath) {     File file = new File(filePath);     if (file == null || !file.exists()) return;     if (file.isFile())     {         file.delete();     }     else     {         File[] arrFiles = file.listFiles();         if (arrFiles.length > 0)         {             for(int i = 0; i < arrFiles.length; i++)             {                 del(arrFiles[i].getAbsolutePath());             }         }         file.delete();     } }

获取文件夹大小 public static long getFolderSize(String dir) {     long size = 0;     File file = new File(dir);     if (!file.exists()) throw new RuntimeException("dir does not exist.");     if (file.isFile()) return file.length();     else     {         String[] arrFileName = file.list();         for (int i = 0; i < arrFileName.length; i++)         {             size += getFolderSize(dir + "/" + arrFileName[i]);         }     }     return size; }

将大文件切分成多个小文件 public static void splitFile(String filePath, long unit) throws IOException {     File file = new File(filePath);     if (!file.exists()) throw new RuntimeException("file does not exist.");     long size = file.length();     if (unit >= size) return;     int count = size % unit == 0 ? (int)(size/unit) : (int)(size/unit) + 1;     String newFile = null;     FileOutputStream fos = null;     FileInputStream fis =null;     byte[] buffer = new byte[(int)unit];     fis = new FileInputStream(file);     long startPos = 0;     String countFile = filePath + "_Count";     PrintWriter writer = new PrintWriter(new FileWriter( new File(countFile)));     writer.println(filePath + "\t" + size);     for (int i = 1; i <= count; i++)     {         newFile = filePath + "_" + i;         startPos = (i - 1) * unit;         System.out.println("Creating " + newFile);         fos = new FileOutputStream(new File(newFile));         int bytesRead = fis.read(buffer, 0, buffer.length);         if (bytesRead != -1)         {             fos.write(buffer, 0, bytesRead);             writer.println(newFile + "\t" + startPos + "\t" + bytesRead);         }         fos.flush();         fos.close();         System.out.println("StartPos:" + i*unit + "; EndPos:" + (i*unit + bytesRead));     }     writer.flush();     writer.close();     fis.close(); }

将多个小文件合并成一个大文件 public static void linkFiles(String countFile) throws IOException {     File file = new File(countFile);     if (!file.exists()) throw new RuntimeException("Count file does not exist.");     BufferedReader reader = new BufferedReader(new FileReader(file));     String line = reader.readLine();     String newFile = line.split("\t")[0];     long size = Long.parseLong(line.split("\t")[1]);     RandomAccessFile raf = new RandomAccessFile(newFile, "rw");     raf.setLength(size);     FileInputStream fis = null;     byte[] buffer = null;     while((line = reader.readLine()) != null)     {         String[] arrInfo = line.split("\t");         fis = new FileInputStream(new File(arrInfo[0]));         buffer = new byte[Integer.parseInt(arrInfo[2])];         long startPos = Long.parseLong(arrInfo[1]);         fis.read(buffer, 0, Integer.parseInt(arrInfo[2]));         raf.seek(startPos);         raf.write(buffer, 0, Integer.parseInt(arrInfo[2]));         fis.close();     }     raf.close(); }

执行外部命令 public static void execExternalCommand(String command, String argument) {     Process process = null;     try     {         process = Runtime.getRuntime().exec(command + " " + argument);         InputStream is = process.getInputStream();         BufferedReader br = new BufferedReader(new InputStreamReader(is));         String line = null;         while((line = br.readLine()) != null)         {             System.out.println(line);         }     }     catch(Exception ex)     {         System.err.println(ex.getMessage());     }     finally     {         if (process != null) process.destroy();     } }