字符串和十六进制数之间的转换

    Java代码实现如下：

package com.csc.stringtobyte;

public class StringToByte{

	public static void main(String[] args) {
		
		String string = new String("hello world!");
		byte[] stringByte = string.getBytes();
		String hexString = bytesToHexString(stringByte);
		System.out.println(hexString);
		byte[] binByte = hexStringToBytes(hexString);
		String result = new String(binByte);
		System.out.println(result);
		
	}
	
	/**
    * Convert byte[] to hex string.这里我们可以将byte转换成int，然后利用Integer.toHexString(int)来转换成16进制字符串。
    * @param src byte[] data
    * @return hex string
    */   
   public static String bytesToHexString(byte[] src){
       StringBuilder stringBuilder = new StringBuilder("");
       if (src == null || src.length <= 0) {
           return null;
       }
       for (int i = 0; i < src.length; i++) {
           int v = src[i] & 0xFF;
           String hv = Integer.toHexString(v);
           if (hv.length() < 2) {
               stringBuilder.append(0);
           }
           stringBuilder.append(hv);
       }
       return stringBuilder.toString();
   }
   /**
    * Convert hex string to byte[]
    * @param hexString the hex string
    * @return byte[]
    */
   public static byte[] hexStringToBytes(String hexString) {
       if (hexString == null || hexString.equals("")) {
           return null;
       }
       hexString = hexString.toUpperCase();
       int length = hexString.length() / 2;
       char[] hexChars = hexString.toCharArray();
       byte[] d = new byte[length];
       for (int i = 0; i < length; i++) {
           int pos = i * 2;
           d[i] = (byte) (charToByte(hexChars[pos]) << 4 | charToByte(hexChars[pos + 1]));
       }
       return d;
   }
   /**
    * Convert char to byte
    * @param c char
    * @return byte
    */
    private static byte charToByte(char c) {
       return (byte) "0123456789ABCDEF".indexOf(c);
   }
}