A functional alternative to an if-else block, using Optional.

ScratchyMcScratch.java

package main;

import java.util.Optional;

import static java.lang.String.format;

public class ScratchyMcScratch {

    public static void main(String[] args) {
        final ScratchyMcScratch mcScratch = new ScratchyMcScratch();
        System.out.println(mcScratch.functional("m")); //M: m
        System.out.println(mcScratch.imperative("m")); //M: m

        System.out.println(mcScratch.functional("mr")); //MR
        System.out.println(mcScratch.imperative("mr")); //MR

        System.out.println(mcScratch.functional("mrmrm")); //mrmrm***
        System.out.println(mcScratch.imperative("mrmrm")); //mrmrm***
    }

    /**
     * Upper cases string if its length is even numbered
     */
    private static Optional<String> first(final String id) {
        if (id.length() % 2 == 0) {
            return Optional.of(id.toUpperCase());
        } else {
            return Optional.empty();
        }
    }

    /**
     * Appends '***' to string if its length is greater than 4
     */
    private static Optional<String> second(final String id) {
        if (id.length() > 4) {
            return Optional.of(id + "***");
        } else {
            return Optional.empty();
        }
    }

    private String functional(final String id) {
        return first(id)
            .map(Optional::of)
            .orElseGet(() -> second(id))
            .orElse(format("M: %s", id));
    }

    private static String first_1(final String id) {
        return first(id).orElse(null);
    }

    private static String second_1(final String id) {
        return second(id).orElse(null);
    }

    private String imperative(final String id) {
        final String first = first_1(id);
        if (first != null) {
            return first;
        }

        final String second = second_1(id);
        if (second != null) {
            return second;
        }

        return format("M: %s", id);
    }
}