记录工作中可能用到的--3 数据之间的转化

最近看行业的通信协议,很是痛苦~~~

不多说了记录一些,以后好找:

关于数值:

1 我们通用的是十进制数,所以在java中 int 在范围内表示十进制的数,那么写一个0x202022;   它表示什么呢?   用十六进制为例子

int a = 100;int b = 0x20;Log.i("lllllllllllllll", a + "");Log.i("lllllllllllllll", b + "");Log.i("lllllllllllllll", Byte.parseByte(a + "") + "");Log.i("lllllllllllllll", Byte.parseByte(b + "") + "");

2先看下结果吧:

3 从结果来看是被解释成十进制的数了,如果一个数超过了数据类型的范围怎么办? 

1 一个方式是用数组来装它了.

4 提供一个string 转化byte数组的方法和 byte数组转回来的方法

public static byte[] toBytes(String value) {   if (value == null || value.trim().length() <= 0) {      return null;   }   int len = 0;   if (value.trim().length() % 2 == 0) {      len = value.trim().length() / 2;   } else {      len = value.trim().length() / 2 + 1;   }   byte[] ret = new byte[len];   for (int i = 0; i < len; i++) {      try {         String temp = value.trim().substring(i * 2, value.length());         if (temp.length() < 2) {            ret[i] = (byte) Integer.parseInt(temp, 16);         } else {            ret[i] = (byte) Integer.parseInt(temp.substring(0, 2),16);         }      } catch (Exception e) {         ret[i] = 0;         e.printStackTrace();      }   }   return ret;}

public static String toHexString(byte[] value, int index, int length) {   if (value == null)      return "";   StringBuffer retBuffer = new StringBuffer();   for (int i = index; i < index+length; i++) {      retBuffer.append(toHexString(value[i]));   }   return retBuffer.toString();}
public static String toHexString(byte value) {   String stmp = Integer.toHexString(value & 0xFF);   return (stmp.length() == 1) ? "0" + stmp : stmp;}

5: 使用方法查看结果;

int a = 100;int b = 0x2020202;Log.i("lllllllllllllll", a + "");Log.i("lllllllllllllll", b + "");Log.i("lllllllllllllll", Arrays.toString(toBytes(a + "")));Log.i("lllllllllllllll", Arrays.toString(toBytes(b + "")));

Log.i("lllllllllllllll", toHexString(toBytes(b + ""), 0, 4));

6转化可能会出些问题,请具体问题具体分析