Creating a UUID from a string with no dashes

Question

How would I create a java.util.UUID from a string with no dashes?

\"5231b533ba17478798a3f2df37de2aD7\" => #uuid \"5231b533-ba17-4787-98a3-f2df37de2aD7\"
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Answer 1

I believe the following is the fastest in terms of performance. It is even slightly faster than Long.parseUnsignedLong version . It is slightly altered code that comes from java-uuid-generator.

 public static UUID from32(
        String id) {
    if (id == null) {
        throw new NullPointerException();
    }
    if (id.length() != 32) {
        throw new NumberFormatException("UUID has to be 32 char with no hyphens");
    }

    long lo, hi;
    lo = hi = 0;

    for (int i = 0, j = 0; i < 32; ++j) {
        int curr;
        char c = id.charAt(i);

        if (c >= '0' && c <= '9') {
            curr = (c - '0');
        }
        else if (c >= 'a' && c <= 'f') {
            curr = (c - 'a' + 10);
        }
        else if (c >= 'A' && c <= 'F') {
            curr = (c - 'A' + 10);
        }
        else {
            throw new NumberFormatException(
                    "Non-hex character at #" + i + ": '" + c + "' (value 0x" + Integer.toHexString(c) + ")");
        }
        curr = (curr << 4);

        c = id.charAt(++i);

        if (c >= '0' && c <= '9') {
            curr |= (c - '0');
        }
        else if (c >= 'a' && c <= 'f') {
            curr |= (c - 'a' + 10);
        }
        else if (c >= 'A' && c <= 'F') {
            curr |= (c - 'A' + 10);
        }
        else {
            throw new NumberFormatException(
                    "Non-hex character at #" + i + ": '" + c + "' (value 0x" + Integer.toHexString(c) + ")");
        }
        if (j < 8) {
            hi = (hi << 8) | curr;
        }
        else {
            lo = (lo << 8) | curr;
        }
        ++i;
    }
    return new UUID(hi, lo);
}