public class Util Reverse 反转 整数、字节

package com.newglobal.dispense.util;

public class Util {
    //按字节反转
    public static int reverseB(int num){
        int ret = 0;
        String str = "" + num;//0123456789L
        int len = str.length()%2 + 1;
        byte[] bt    = str.getBytes();

        for (int i = 0; i < 16 ; i++){
            ret |= (num & (1 << i)) << (31-2*i);//先找到低2位，然后移动到对应的高2位，再与要返回的结果 或
            System.out.println(num);
            System.out.println(num & (1 << i));
            //System.out.println(ret);
            ret |= (num & (0x80000000 >> i*2) ) >> (31-2*i);//再找到高2位，然后移动到对应的低2位，再与要返回的结果 或
        }
        return ret;
    }
    //按字节反转
    public static int reverseByte(int num){
        int ret = 0;       
        ret += num << 24;       
        ret += ((num << 16 | 0xFFFFFF) >> 24) * 0x10000;       
        ret += ((num << 8 | 0xFFFFFF) >> 24) * 0x100;       
        ret += (num | 0xFFFFFF) >> 24;
        return ret;
    }
    //    按字节反转
    public static short reverseShort(short num){
        short ret = 0;       
        ret += num << 8;
        System.out.println("ret1="+ret);
        ret += (num | 0xFF) >> 8;       
        System.out.println("ret2="+ret);   
        return ret;
    }

    //按字节反转一个int整数
    public static int reverseInt(int num){
            int ret = 0;       
            ret += ((num << 24) & 0xFF) * 0x1000000;
            ret += ((num << 16) & 0xFF) * 0x10000;
            ret += ((num << 8 ) & 0xFF) * 0x100;       
            ret += (num         & 0xFF);
            return ret;
        }
    public static void main(String[] args) {
        int ii = 0x12345678;//7ffffffe;//2147483646;
        int nn = reverseByte(ii);
        short ss = 0x3827;
        short mm = reverseShort(ss);
        int i = reverseInt(ii);
        System.out.println("reverseShort="+mm);
        System.out.println("reverseInt="+i);
    }

    //按字节反转一个int整数
    /*public int reverseInt(int num){
        int ret = 0;       
        ret += num << 24;       
        ret += ((num << 16 | 0xFFFFFF) >> 24) * 0xFFFF;       
        ret += ((num << 8 | 0xFFFFFF) >> 24) * 0xFF;       
        ret += (num | 0xFFFFFF) >> 24;
        return ret;
    }*/

}