ethereum address checker

AddressChecker.java

package demo;

import java.math.BigInteger;
import java.util.Arrays;

import org.web3j.crypto.Hash;
import org.web3j.utils.Numeric;

public class AddressChecker {

    public static String checkedAddress(final String address) {
        final String cleanAddress = Numeric.cleanHexPrefix(address).toLowerCase();
        //
        StringBuilder o = new StringBuilder();
        String keccak = Hash.sha3String(cleanAddress);
        char[] checkChars = keccak.substring(2).toCharArray();

        char[] cs = cleanAddress.toLowerCase().toCharArray();
        for (int i = 0; i < cs.length; i++) {
            char c = cs[i];
            c = (Character.digit(checkChars[i], 16) & 0xFF) > 7 ? Character.toUpperCase(c) : Character.toLowerCase(c);
            o.append(c);
        }
        return Numeric.prependHexPrefix(o.toString());
    }

    public static boolean isCheckedAddress(final String address) {
        return Numeric.prependHexPrefix(address).equals(checkedAddress(address));
    }

    public static void main(String[] args) {
        Arrays.asList("00Be17C6aD2738fb20B80f290C8fa1F4F8aB5902", // valid address
                "0x00Be17C6aD2738fb20B80f290C8fa1F4F8aB5902", // valid address
                "00be17C6aD2738fb20B80f290C8fa1F4F8aB5902", // invalid address
                "0x00be17C6aD2738fb20B80f290C8fa1F4F8aB5902"// invalid address
        ).forEach(addr -> {
            System.out.printf("%s => %s === %s\n", addr, checkedAddress(addr), isCheckedAddress(addr));
        });
    }

}

Ethereum EIP-55 Mixed-case checksum address encoding

• EIP-55 https://github.com/ethereum/EIPs/blob/master/EIPS/eip-55.md

dependency:

• web3j https://github.com/web3j/web3j

igen,de ez meg csak proposal azóta rájöttem

tényleg nincs semmilyen checksumming by default

I think a combination between try to convert it to big integer and your code is better.
For input 0xXxxXxxxXXXXxxxXxxXxXXxxxxxxxxxxXxXXxxxXx it still passed.