public static char reHex(byte[] content, int len) {
        byte[] bs = new byte[len];
        for (int i=0; i<len; i++) bs[i] = content[i];
        String s = new String(bs);
        int x = Integer.parseInt(s, 16);
        return (char)x;
    }
    
    public static void main(String[] args) {
        //测试
        byte[] bs = new byte[2];
        bs[0] = '6';
        bs[1] = '4';
        System.out.println(reHex(bs,2));
    }

------解决方案--------------------
public class Ascii2Number { 
   public static void main(String[] args) { 
     System.out.println(toAsciiHexCode( ': ') ); 
     System.out.println(toAsciiHexCode( "toAsciiHexCode ") ); 
   } 
  
   private static String toAsciiHexCode(String str) { 
     if (null == str) return  " "; 
  
     StringBuilder builder = new StringBuilder(); 
     for (int i=0; i  < str.length(); i++) { 
       builder.append(toAsciiHexCode(str.charAt(i))).append( "  "); 
     } 
  
     return builder.toString(); 
   } 
   private static String toAsciiHexCode(char ch) { 
     return Integer.toHexString(48 + ch -  '0 ').toUpperCase(); 
   } 
 } 
  
  
 3A 
 74 6F 41 73 63 69 69 48 65 78 43 6F 64 65

------解决方案--------------------

我理解错你的意思了，其实你只是要个ASCII码而已，这个很容易实现。2楼给出的就是解决方案了。