java读取文件

  1 java8读取文本文件
  2 
  3         
  4     public static void java8ReadFileLines(String fileName) throws IOException {
  5         List lineList = Files.readAllLines(Paths.get(fileName), StandardCharsets.UTF_8);
  6 
  7         for(String line:lineList){
  8             System.out.println(line);
  9         }
 10     }    
 11     
 12         
 13         
 14 一行一行地读取文件
 15 
 16 
 17     public static void readFileByLines(String fileName) {
 18         File file = new File(fileName);
 19         BufferedReader reader = null;
 20         try {
 21             reader = new BufferedReader(new FileReader(file));
 22             String line = null;
 23             while((line=reader.readLine())!=null ) {
 24                 System.out.println(line);
 25             }
 26         }catch (IOException e) {
 27 
 28         }finally {
 29             if(reader!=null) {
 30                 try{
 31                     reader.close();
 32                 }catch (IOException e) {
 33                     ;
 34                 }
 35             }
 36         }
 37     }    
 38     
 39     
 40     
 41 一次读取多个字符
 42 
 43 
 44     public static void readFileByMultiChars(String fileName) {
 45         File file = new File(fileName);
 46         try{
 47             InputStreamReader inputStreamReader = new InputStreamReader(new FileInputStream(file));
 48 
 49             char[] tempChars = new char[30];
 50 
 51             int readCount = 0;
 52             while((readCount=inputStreamReader.read(tempChars))!=-1) {
 53                 if(readCount==tempChars.length) {
 54                     System.out.println(tempChars);
 55                 }else{
 56                     System.out.println(Arrays.copyOf(tempChars, readCount));
 57                 }
 58             }
 59 
 60 
 61             inputStreamReader.close();
 62         }catch(Exception e) {
 63             e.printStackTrace();
 64         }
 65     }    
 66 
 67 
 68         
 69 一个字符一个字符地读取
 70 
 71 
 72     public static void readFileByChars(String fileName) {
 73         File file = new File(fileName);
 74         try{
 75             InputStreamReader inputStreamReader = new InputStreamReader(new FileInputStream(file));
 76 
 77             int tempChar;
 78 
 79             while((tempChar=inputStreamReader.read())!=-1) {
 80                 System.out.println((char)tempChar);
 81             }
 82 
 83 
 84             inputStreamReader.close();
 85         }catch(Exception e) {
 86             e.printStackTrace();
 87         }
 88     }        
 89 
 90 
 91         
 92 java8读取字节 超级简单
 93 
 94 
 95     public static byte[] java8ReadBytes(String fileName) throws IOException {
 96         return Files.readAllBytes(Paths.get(fileName));
 97     }
 98 
 99 
 
 一个字节一个字节地读取
 
 
    public static void readFileByOneByte(String fileName) {
         File file = new File(fileName);
         InputStream inputStream = null;
 
         try{
             inputStream = new FileInputStream(file);
             int tempByte;
             while( (tempByte=inputStream.read())!=-1) {
                 System.out.println(tempByte);
             }
 
             inputStream.close();
         }catch (IOException e) {
             System.out.println(e);
         }
 
     }
     
     
  
 一个字节一个字节读取到ByteBuffer
 
 
     public static byte[] readFileByOneByteToBuffer(String fileName) {
 
 
         ByteBuffer byteBuffer = ByteBuffer.allocate(1024 * 1024);
 
         File file = new File(fileName);
         InputStream inputStream = null;
 
         try{
             inputStream = new FileInputStream(file);
             int tempByte;
             while( (tempByte=inputStream.read())!=-1) {
                 byteBuffer.put((byte)tempByte);
             }
 
             inputStream.close();
         }catch (IOException e) {
             System.out.println(e);
         }
 
         byteBuffer.flip();
         System.out.println("one limit:" + byteBuffer.limit());
         byte[] result = new byte[byteBuffer.limit()];
         byteBuffer.get(result);
 
         return result;
 
 
     }
     
     
     
 多个字节进行读取
 
 
     public static void readFileByMultiBytes(String fileName) {
 
         File file = new File(fileName);
         InputStream inputStream = null;
 
         try {
             byte[] bytes = new byte[50];
             int byteRead = 0;
             inputStream = new FileInputStream(fileName);
 
             while( (byteRead = inputStream.read(bytes))!=-1 ) {
                 System.out.println(byteRead);
             }
         }catch(IOException e) {
             System.out.println(e);
         }finally {
             if(inputStream!=null) {
                 try{
                     inputStream.close();
                 }catch(IOException e){
                     System.out.println("iput stream close exception" +  e);
                 }
             }
         }
     }
     
     
   
 读取多个字节到ByteBuffer
 
 
     public static byte[] readFileByMultiBytesToBuffer(String fileName) {
 
         ByteBuffer byteBuffer = ByteBuffer.allocate(1024*1024);
         InputStream inputStream = null;
 
         try {
             byte[] bytes = new byte[50];
             int byteRead = 0;
             inputStream = new FileInputStream(fileName);
 
             int count = 0;
             while( (byteRead = inputStream.read(bytes))!=-1 ) {
                 byteBuffer.put(bytes, 0, byteRead);
                 count+=byteRead;
             }
 
             System.out.println("readCount:"+count);
         }catch(IOException e) {
             System.out.println(e);
         }finally {
             if(inputStream!=null) {
                 try{
                     inputStream.close();
                 }catch(IOException e){
                     System.out.println("iput stream close exception" +  e);
                 }
             }
         }
 
         byteBuffer.flip();
         System.out.println("multi limit:" + byteBuffer.limit());
         byte[] result = new byte[byteBuffer.limit()];
         byteBuffer.get(result);
 
         return result;
     }