如何读字节从输入流取bit作位运算(JAVA实现)

在以下是笔者在遇到取bit位运算，源码如下： 



 



package com.bit;



import java.io.ByteArrayInputStream;

import java.io.DataInputStream;

import java.io.IOException;





public class BitTest {

 

   byte[] content = {(byte)9,(byte)111,(byte)120,(byte)32};

     

 public  String readBitYear(byte[] bt) throws IOException {

  byte[] tmp = bt;

    byte a = new DataInputStream(new    ByteArrayInputStream(tmp)).readByte();;

  //int aa =  (a & 0xfc); 

  int aa = a >>2<<2;

  aa += 2000;

  String year = Integer.toString(aa);

  return year; 

    }

 

 public  String readBitMoth(byte[] bt) throws IOException {

  byte[] tmp = bt;

    int b = (int)new DataInputStream(new   ByteArrayInputStream(tmp)).readShort();

  int bb =  b & 0x03C0;

  bb = bb >> 6;

  String mon = Integer.toString(bb);

  while (mon.length()<2) {

   mon = "0"+mon;

  } 

  return mon;

    }

 

 public  String readBitDay(byte[] bt) throws IOException {

  byte[] tmp = bt;

    int c = (int)new DataInputStream(new ByteArrayInputStream(tmp)).readShort();

  int cc =  c & 0x003E;

  cc = cc >> 1;

  String day = Integer.toString(cc);

  while (day.length()<2) {

   day = "0"+day;

  }

  return day;

    }

 

 public  String readBithour(byte[] bt) throws IOException {

  byte[] tmp = bt;

    DataInputStream tmp_dis = new DataInputStream(new ByteArrayInputStream(tmp));

  tmp_dis.readByte();

  int d1 = tmp_dis.readShort();    

  int dd =  d1 & 0x1f0;

  dd = dd >> 4;     

  String hour = Integer.toString(dd);

  while (hour.length()<2) {

   hour = "0"+hour;

  } 

  return hour;

    }

 

 public  String readBitmin(byte[] bt) throws IOException {

  byte[] tmp = bt;

    DataInputStream tmp_dis = new DataInputStream(new ByteArrayInputStream(tmp));

  tmp_dis.readShort();

  int e = tmp_dis.readShort();    

  int ee =  e & 0xfc0;

  ee = ee >> 6;     

  String min = Integer.toString(ee);

  while (min.length()<2) {

   min = "0"+min;

  } 

  return min;

    }

 

 public  String readBitsec(byte[] bt) throws IOException {

  byte[] tmp = bt;

    DataInputStream tmp_dis = new DataInputStream(new ByteArrayInputStream(tmp));

  tmp_dis.readShort();

  int f = tmp_dis.readShort();    

  int ff =  f & 0x3f;   

  String sec = Integer.toString(ff);

  while (sec.length()<2) {

   sec = "0"+sec;

  }

  return sec;

    }

 

 

 /**

  * @param args

  * @throws IOException 

  */

 public static void main(String[] args) throws IOException {

  // TODO Auto-generated method stub  

  BitTest bittest = new BitTest();

   String year = bittest.readBitYear(bittest.content);

  String month = bittest.readBitMoth(bittest.content);

  String day = bittest.readBitDay(bittest.content);

  String hour = bittest.readBithour(bittest.content);

  String min = bittest.readBitmin(bittest.content);

  String sec = bittest.readBitsec(bittest.content);

  System.out.println("years :" + year);

  System.out.println("months :" + month);

  System.out.println("days :" + day);

  System.out.println("hours :" + hour);

  System.out.println("mins :" + min);

  System.out.println("secs :" + sec);  

 }