Hashmap does not work with int, char [duplicate]

Answer 1

Generics can't use primitive types in the form of keywords.

Use

public HashMap buildMap(String letters)
{
    HashMap checkSum = new HashMap();

    for ( int i = 0; i < letters.length(); ++i )
    {
        checkSum.put(letters.charAt(i), primes[i]);
    }

    return checkSum;
}

Updated: With Java 7 and later, you can use the diamond operator.

HashMap checkSum = new HashMap<>();