java 基础知识之IO总结

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();}

使用BufferedInputStream读取文件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();  }}