org.kiwiproject.base.KiwiObjects Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of kiwi Show documentation

Kiwi is a utility library. We really like Google's Guava, and also use Apache Commons. But if they don't have something we need, and we think it is useful, this is where we put it.

There is a newer version: 4.5.2

Show newest version

package org.kiwiproject.base;

import static java.util.Objects.nonNull;

import lombok.experimental.UtilityClass;

import java.util.Arrays;
import java.util.Objects;
import java.util.Optional;
import java.util.function.Supplier;

/**
 * Utilities for any object which are not in {@link java.util.Objects} or {@link com.google.common.base.MoreObjects}.
 */
@UtilityClass
public class KiwiObjects {

    /**
     * Return the first non-null object, or {@code null} if all are null.
     *
     * @param first  the first object
     * @param second the second object
     * @param rest   zero or more additional objects
     * @param     the type of objects
     * @return the first non-null object or null if all are null
     */
    @SafeVarargs
    public static  T firstNonNullOrNull(T first, T second, T... rest) {
        return firstNonNull(first, second, rest).orElse(null);
    }

    /**
     * Return the first supplied non-null object, or {@code null} if all all suppliers return null.
     *
     * @param first  the first object supplier
     * @param second the second object supplier
     * @param rest   zero or more additional object suppliers
     * @param     the type of objects
     * @return the first non-null supplied object or null if all suppliers return null
     * @implNote once a non-null object is supplied, no further suppliers are called
     */
    @SafeVarargs
    public static  T firstSuppliedNonNullOrNull(Supplier first, Supplier second, Supplier... rest) {
        return firstSuppliedNonNull(first, second, rest).orElse(null);
    }

    /**
     * Return an {@link Optional} containing the first non-null object, or an empty {@link Optional} if all are null.
     *
     * @param first  the first object
     * @param second the second object
     * @param rest   zero or more additional objects
     * @param     the type of objects
     * @return an optional containing the first non-null object or empty optional if all are null
     */
    @SafeVarargs
    public static  Optional firstNonNull(T first, T second, T... rest) {
        if (nonNull(first)) {
            return Optional.of(first);
        }

        if (nonNull(second)) {
            return Optional.of(second);
        }

        return Arrays.stream(rest)
                .filter(Objects::nonNull)
                .findFirst();
    }

    /**
     * Return an {@link Optional} containing the first non-null object, or an empty {@link Optional} if all suppliers
     * return null.
     *
     * @param first  the first object supplier
     * @param second the second object supplier
     * @param rest   zero or more additional object suppliers
     * @param     the type of objects
     * @return an optional containing the first non-null supplied object or empty optional if all suppliers return null
     * @implNote once a non-null object is supplied, no further suppliers are called
     */
    @SafeVarargs
    public static  Optional firstSuppliedNonNull(Supplier first, Supplier second, Supplier... rest) {
        var firstT = first.get();
        if (nonNull(firstT)) {
            return Optional.of(firstT);
        }

        var secondT = second.get();
        if (nonNull(secondT)) {
            return Optional.of(secondT);
        }

        return Arrays.stream(rest)
                .map(Supplier::get)
                .filter(Objects::nonNull)
                .findFirst();
    }
}