How do I check if a string is a valid md5 or sha1 checksum string

Question

I don't want to calculate a file's checksum, just to know if a given string is a valid checksum

Answer 1

SHA1 verifier:

public boolean isValidSHA1(String s) {
    return s.matches("^[a-fA-F0-9]{40}$");
}

MD5 verifier:

public boolean isValidMD5(String s) {
    return s.matches("^[a-fA-F0-9]{32}$");
}

Answer 2

Any 160-bit sequence is a possible SHA1 hash. Any 128-bit sequence is a possible MD5 hash.

If you're looking at the hex string representations of them, then a sha1 will look like 40 hexadecimal digits, and an md5 will look like 32 hexadecimal digits.

Answer 3

MD5 verifier:

public boolean isValidMD5(String s) {
return s.matches("[a-fA-F0-9]{32}");}

And remove "-" of the string value.

Answer 4

RegExp SHA-1

public static final String SHA_1 = "^([0-9A-Fa-f]{2}[:]){19}([0-9A-Fa-f]{2})$";

public boolean isValidSHA1(String s) {
    return s.matches(SHA_1);
}

boolean isValidSHA1 = isValidSHA1("12:45:54:3A:99:24:52:EA...");