Conversion in Java -- String, Hex, Bytes and Bits.

 

/**
 * This class contains the conversions among String, Hex, Bytes and Bits.
 */
public class Conversion {

    /**
     * Return the hexadecimal format of a plain text string.
     *
     * @param strValue
     * @return
     */  
    public static String stringToHex(String strValue) {
        byte byteData[] = null;
        int intHex = 0;
        String strHex = "";
        String strReturn = "";
        try {
            byteData = strValue.getBytes("ISO8859-1");
            for (int i=0;i<byteData.length;i++)
            {
                intHex = (int)byteData[i];
                if (intHex<0)
                    intHex += 256;
                if (intHex<16)
                    strHex += "0" + Integer.toHexString(intHex).toUpperCase();
                else
                    strHex += Integer.toHexString(intHex).toUpperCase();
            }
            strReturn = strHex;

        }
        catch (Exception ex) {
            ex.printStackTrace();
        }
        return strReturn;
    }

    /**
     * Convert a hexadecimal string to the plain text string.
     *
     * @param strValue
     * @return
     */
    public static String hexToString(String strValue) {
        int len = strValue.length() / 2;
        String strReturn = "";
        String strHex = "";
        int intHex = 0;
        byte byteData[] = new byte[len];
        try {
            for (int i = 0; i < len; i++) {
                strHex = strValue.substring(0, 2);
                strValue = strValue.substring(2);
                intHex = Integer.parseInt(strHex, 16);
                if (intHex > 128)
                    intHex = intHex - 256;
                byteData[i] = (byte) intHex;
            }
            strReturn = new String(byteData,"ISO8859-1");
        }
        catch (Exception ex) {
            ex.printStackTrace();
        }
        return strReturn;
    }

    /**
     * Convert a byte to bits.
     *
     * @param b
     * @return
     */
    public static String byteToBits(byte b) {
        StringBuffer buf = new StringBuffer();
        for (int i=0; i<8; i++)
            buf.append((int)(b>>(8-(i+1)) & 0x0001));
        return buf.toString();
    }

    /**
     * Convert a hex string to bytes array.
     *
     * @param str
     * @return
     */
    public static byte[] hexToBytes(String str) {
        if (str==null) {
            return null;
        } else if (str.length() < 2) {
            return null;
        } else {
            int len = str.length() / 2;
            byte[] buffer = new byte[len];
            for (int i=0; i<len; i++) {
                buffer[i] = (byte) Integer.parseInt(
                        str.substring(i*2,i*2+2),16);
            }
            return buffer;
        }

    }


    /**
     * Convert a bytes array to hex string.
     * @param data
     * @return
     */
    public static String bytesToHex(byte[] data) {
        StringBuilder sb = new StringBuilder();

        for (int i=0; i<data.length; i++) {
            int num = Integer.valueOf(byteToBits(data[i]), 2);
            if (num < 16) {
                sb.append("0" + Integer.toHexString(num));
            } else {
                sb.append(Integer.toHexString(num));
            }
        }

        return sb.toString().toUpperCase();
    }

}