HashMap with reduce

import java.util.HashMap;
import java.util.stream.IntStream;

class Scrabble {

    private final int savedScore;
    private final static HashMap < Integer, Integer > lookup = new HashMap(26);
    private final static String[] letters = {
        "AEIOULNRST",
        "DG",
        "BCMP",
        "FHVWY",
        "K",
        "JX",
        "QZ"
    };
    private final static int[] scores = {
        1,
        2,
        3,
        4,
        5,
        8,
        10
    };

    static {
        IntStream.range(0, letters.length)
            .forEach(index -> letters[index].chars().forEach(letter -> lookup.put(letter, scores[index])));
    }

    Scrabble(String word) {
        savedScore = word.toUpperCase().chars().reduce(0, (score, letter) -> score + lookup.get(letter));
    }

    int getScore() {
        return savedScore;
    }

}

This approach starts by importing from packages for what is needed.

A private final variable is defined to be returned by the getScore() method. It is private because it does not need to be directly accessed from outside the class, and it is final because its value does not need to be changed once it is set.

Several private final static variables are then defined:

• a HashMap to hold the lookups of the scores for the letters
• a String array of the letters grouped by their common score
• an int array of the scores for the letters

They are static because they don't need to differ between object instantiations, so they can belong to the class itself.

In a static block, the IntStream.range() method is called to iterate an index from 0 up to but including the length of the array of letters. In a forEach() method, each index value is passed into a lambda which calls the chars{} method on each string at the index of the letters array. In another forEach, each letter is passed into a lambda that adds the letter and its corresponding score to the HashMap. This works because the groups of letters and their scores are at the same index in their respective arrays.

In the constructor, chars() is called on the uppercased word and chained to the reduce() method. The accumulator is initialized to 0, and the accumulator and each letter is passed to a lambda that adds the score looked up from the HashMap for the letter. The score variable is set to the value returned from reduce(), which is the value of its accumulator.