byteArray <==> Hex

 一些算法摘录自：

http://stackoverflow.com/questions/332079/in-java-how-do-i-convert-a-byte-array-to-a-string-of-hex-digits-while-keeping-le

 

http://rgagnon.com/javadetails/java-0596.html

 

http://stackoverflow.com/questions/140131/convert-a-string-representation-of-a-hex-dump-to-a-byte-array-using-java

 

 发现经常需要使用这个函数，故放在blog上用于以后查看

 

  一：字节数组转换到16进制形式的字符串

   1：利用Integer的toHexString

 /**
     * 字节数组转换成十六进制字符串
     *
     * @param b 字节数组
     *
     * @return 十六进制字符串
     */
    public static final String byte2hex(byte[] b) {
        String hs   = "";
        String stmp = "";

        for (int i = 0; i < b.length; i++) {
            stmp = Integer.toHexString(b[i] & 0xFF);

            if (stmp.length() == 1) {
                hs += "0" + stmp;
            } else {
                hs += stmp;
            }
        }

        return hs.toUpperCase();
    }

 

  2：利用BigInteger 和String.format

 

public static String toHex(byte[] bytes) {
	    BigInteger bi = new BigInteger(1, bytes);
	    return String.format("%0" + (bytes.length << 1) + "X", bi);
}

 

  3:利用BigInteger

 

public static String toHex(byte[] bytes) {
		BigInteger bi = new BigInteger(1, bytes);
	    String result = bi.toString(16);
	    if (result.length() % 2 != 0) {
	        return "0" + result;
	    }
	    return result.toUpperCase();

}

 

 4.1： & 神奇的数

 

public static String toHex(byte[] b) throws Exception {
		  String result = "";
		  for (int i=0; i < b.length; i++) {
		    result +=
		          Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring( 1 );
		  }
		  return result.toUpperCase();
}

 

4.2 : + 神奇的数 （和上一个有关）

 

public static String toHex(byte[]bytes) {
	    StringBuilder sb = new StringBuilder(bytes.length*2);
	    for(byte b: bytes)
	      sb.append(Integer.toHexString(b+0x800).substring(1));
	    return sb.toString().toUpperCase();
}

 

 

5.1：映射表 移位 &

public static String toHex( byte [] raw ) {
	 String HEXES = "0123456789ABCDEF";
	    if ( raw == null ) {
	      return null;
	    }
	    final StringBuilder hex = new StringBuilder( 2 * raw.length );
	    for ( final byte b : raw ) {
	      hex.append(HEXES.charAt((b & 0xF0) >> 4))
	         .append(HEXES.charAt((b & 0x0F)));
	    }
	    return hex.toString();
}

5.1 :映射表 除法 取模

public static String toHex(byte[] bytes) {
	    char[] hexArray = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
	    char[] hexChars = new char[bytes.length * 2];
	    int v;
	    for ( int j = 0; j < bytes.length; j++ ) {
	        v = bytes[j] & 0xFF;
	        hexChars[j*2] = hexArray[v/16];
	        hexChars[j*2 + 1] = hexArray[v%16];
	    }
	    return new String(hexChars);
}

 

 

6：String.format

 

static String toHex(byte[] digest) {
	    StringBuilder sb = new StringBuilder();
	    for (byte b : digest) {
	        sb.append(String.format("%1$02X", b));
	    }

	    return sb.toString();
}

 

 

   二：十六进制字符串转为字节数组，上一个的逆过程

  /**
     * 十六进制字符串转换成字节数组
     *
     * @param hex 十六进制字符串
     *
     * @return 字节数组
     *
     * @throws IllegalArgumentException
     */
    public static final byte[] hex2byte(String hex) throws IllegalArgumentException {
        if (hex.length() % 2 != 0) {
            throw new IllegalArgumentException();
        }

        char[] arr = hex.toCharArray();
        byte[] b = new byte[hex.length() / 2];

        for (int i = 0, j = 0, l = hex.length(); i < l; i++, j++) {
            String swap    = "" + arr[i++] + arr[i];
            int    byteint = Integer.parseInt(swap, 16) & 0xFF;

            b[j] = new Integer(byteint).byteValue();
        }

        return b;
    }

 

 新发现，其实JAVA中有提供这一函数，还可以偷窥其实现

 

 javax.xml.bind.annotation.adapters.HexBinaryAdapter;

  public byte[] unmarshal(String s) {
        if(s==null)     return null;
        return DatatypeConverter.parseHexBinary(s);
  }

  public String marshal(byte[] bytes) {
        if(bytes==null)     return null;
        return DatatypeConverter.printHexBinary(bytes);
  }

 

 

其实很早以前看到一个实现更加简便的，但是忘了是什么了，有同学发现了告诉我下。