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

Answer: 
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}$");
}

```
MD5 verifier:

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

```

And remove "-" of the string value.