JAVA读取文件方法大全

public static void readFileByBytes(String fileName) {
         File file = new File(fileName);
         InputStream in = null;
         try {
             System.out.println("以字节为单位读取文件内容，一次读一个字节：");
             // 一次读一个字节
             in = new FileInputStream(file);
             int tempbyte;
             while ((tempbyte = in.read()) != -1) {   
                 System.out.write(tempbyte);
             }
             in.close();   
         } catch (IOException e) {
             e.printStackTrace();
             return;
         }
         try {
             System.out.println("以字节为单位读取文件内容，一次读多个字节：");
             // 一次读100个字节
             byte[] tempbytes = new byte[100];
             int byteread = 0;
             in = new FileInputStream(fileName);
             ReadFromFile.showAvailableBytes(in);
             // 读入多个字节到字节数组中，byteread为一次读入的字节数
             while ((byteread = in.read(tempbytes)) != -1) {
                 System.out.write(tempbytes, 0, byteread);
             }
         } catch (Exception e1) {
             e1.printStackTrace();
         } finally {
             if (in != null) {
                 try {
                     in.close();
                 } catch (IOException e1) {
                 }
             }
         }
     }

二、按字符读取文件内容

        
     public static void readFileByChars(String fileName) {   
         File file = new File(fileName);   
         Reader reader = null;   
         try {   
             System.out.println("以字符为单位读取文件内容，一次读一个字节：");   
             // 一次读一个字符   
             reader = new InputStreamReader(new FileInputStream(file));   
             int tempchar;   
             while ((tempchar = reader.read()) != -1) {   
                 // 对于windows下，\r\n这两个字符在一起时，表示一个换行。   
                 // 但如果这两个字符分开显示时，会换两次行。   
                 // 因此，屏蔽掉\r，或者屏蔽\n。否则，将会多出很多空行。   
                 if (((char) tempchar) != '\r') {   
                     System.out.print((char) tempchar);   
                 }   
             }   
             reader.close();   
         } catch (Exception e) {   
             e.printStackTrace();   
         }   
         try {   
             System.out.println("以字符为单位读取文件内容，一次读多个字节：");   
             // 一次读多个字符   
             char[] tempchars = new char[30];   
             int charread = 0;   
             reader = new InputStreamReader(new FileInputStream(fileName));   
             // 读入多个字符到字符数组中，charread为一次读取字符数   
             while ((charread = reader.read(tempchars)) != -1) {   
                 // 同样屏蔽掉\r不显示   
                 if ((charread == tempchars.length)   
                         && (tempchars[tempchars.length - 1] != '\r')) {   
                     System.out.print(tempchars);   
                 } else {   
                     for (int i = 0; i < charread; i++) {   
                         if (tempchars[i] == '\r') {   
                             continue;   
                         } else {   
                             System.out.print(tempchars[i]);   
                         }   
                     }   
                 }   
             }   
    
         } catch (Exception e1) {   
             e1.printStackTrace();   
         } finally {   
             if (reader != null) {   
                 try {   
                     reader.close();   
                 } catch (IOException e1) {   
                 }   
             }   
         }   
     }  

三、按行读取文件内容

        
     public static void readFileByLines(String fileName) {   
         File file = new File(fileName);   
         BufferedReader reader = null;   
         try {   
             System.out.println("以行为单位读取文件内容，一次读一整行：");   
             reader = new BufferedReader(new FileReader(file));   
             String tempString = null;   
             int line = 1;   
             // 一次读入一行，直到读入null为文件结束   
             while ((tempString = reader.readLine()) != null) {   
                 // 显示行号   
                 System.out.println("line " + line + ": " + tempString);   
                 line++;   
             }   
             reader.close();   
         } catch (IOException e) {   
             e.printStackTrace();   
         } finally {   
             if (reader != null) {   
                 try {   
                     reader.close();   
                 } catch (IOException e1) {   
                 }   
             }   
         }   
     }  

四、随机读取文件内容

        
     public static void readFileByRandomAccess(String fileName) {   
         RandomAccessFile randomFile = null;   
         try {   
             System.out.println("随机读取一段文件内容：");   
             // 打开一个随机访问文件流，按只读方式   
             randomFile = new RandomAccessFile(fileName, "r");   
             // 文件长度，字节数   
             long fileLength = randomFile.length();   
             // 读文件的起始位置   
             int beginIndex = (fileLength > 4) ? 4 : 0;   
             // 将读文件的开始位置移到beginIndex位置。   
             randomFile.seek(beginIndex);   
             byte[] bytes = new byte[10];   
             int byteread = 0;   
             // 一次读10个字节，如果文件内容不足10个字节，则读剩下的字节。   
             // 将一次读取的字节数赋给byteread   
             while ((byteread = randomFile.read(bytes)) != -1) {   
                 System.out.write(bytes, 0, byteread);   
             }   
         } catch (IOException e) {   
             e.printStackTrace();   
         } finally {   
             if (randomFile != null) {   
                 try {   
                     randomFile.close();   
                 } catch (IOException e1) {   
                 }   
             }   
         }   
     }