Decode hexadecimal-encoded string and return raw byte array. - Java java.lang

Java examples for java.lang:byte Array to String

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Description

Decode hexadecimal-encoded string and return raw byte array.

Demo Code


//package com.java2s;

public class Main {
    public static void main(String[] argv) throws Exception {
        String hex = "java2s.com";
        System.out.println(java.util.Arrays.toString(fromHex(hex)));
    }//from   w ww.  j a  v  a 2 s  . c om

    /**
     * Decode hexadecimal-encoded string and return raw byte array.
     * Important note: This method preserves leading 0 filled bytes on the
     * conversion process, which is important for cryptographic operations
     * in dealing with things like keys, initialization vectors, etc. For
     * example, the string "0x0000face" is going to return a byte array
     * whose length is 4, not 2.
     *
     * @param   hex
     *         Hexadecimal-encoded string, with or without leading "0x".
     * @return   The equivalent byte array.
     */
    public static byte[] fromHex(String hex) {

        if (hex == null || hex.trim().isEmpty()) {
            throw new IllegalArgumentException(
                    "Parameter \"hex\" cannot be "
                            + "null or an empty string");
        }

        if (hex.length() % 2 == 1) {
            throw new IllegalArgumentException("Invalid hex string \""
                    + hex + "\" (not enough bytes)");
        }

        if (hex.startsWith("0x")) {
            hex = hex.substring(2);
        }

        int length = hex.length() / 2;
        byte[] result = new byte[length];
        for (int i = 0; i < length; i++) {
            String pair = hex.substring(i * 2, (i * 2) + 2);
            result[i] = (byte) (Integer.parseInt(pair, 16));
        }

        return result;
    }
}

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