AddressValidator.java

import java.util.zip.CRC32;

public class AddressValidator {
  public static byte[] base16Decode(String s) {
    byte[] buf = new byte[s.length() / 2];
    for (int i = 0; i < s.length() / 2; ++i) {
      byte hi = Byte.parseByte(s.substring(i * 2, (i * 2) + 1), 16);
      byte lo = Byte.parseByte(s.substring((i * 2) + 1, (i * 2) + 2), 16);
      buf[i] = (byte)((hi << 4) | lo);
    }
    return buf;
  }

  public static boolean addressValidate(String addr) {
    byte[] buf = AddressValidator.base16Decode(addr);

    CRC32 hasher = new CRC32();
    hasher.update(buf, 4, buf.length - 4);
    long hash = hasher.getValue();

    return hash == ((Byte.toUnsignedLong(buf[0]) << 24) | (Byte.toUnsignedLong(buf[1]) << 16) | (Byte.toUnsignedLong(buf[2]) << 8) | Byte.toUnsignedLong(buf[3]));
  }
}