OptionalComparator.java

package com.rwe.st.cao.gas.attila.util;

import java.util.Comparator;
import java.util.Optional;

/**
 * Comparator utils for {@see Optional} types.
 */
public final class OptionalComparator {

    private OptionalComparator() {
    }

    public static <T extends Comparable<T>> Comparator<Optional<T>> absentFirst() {
        return absentFirst(Comparator.<T>naturalOrder());
    }

    public static <T extends Comparable<T>> Comparator<Optional<T>> absentFirst(Comparator<T> comparator) {
        return Comparator.comparing(x -> x.orElse(null), Comparator.nullsFirst(comparator));
    }

    public static <T extends Comparable<T>> Comparator<Optional<T>> absentLast() {
        return absentLast(Comparator.<T>naturalOrder());
    }

    public static <T extends Comparable<T>> Comparator<Optional<T>> absentLast(Comparator<T> comparator) {
        return Comparator.comparing(x -> x.orElse(null), Comparator.nullsLast(comparator));
    }

}