Java List Last Item getLast(final List list)

Description

Gets the last element of the list.

License

Open Source License

Parameter

Parameter	Description
T	The type of element in the list.
list	The list to get the last element from.

Return

The last element from the list, if one exists. Otherwise, null.

Declaration

public static <T> T getLast(final List<? extends T> list) 

Method Source Code

//package com.java2s;
/*/*ww  w . j  a  v a 2 s  . c o m*/
 * File:                CollectionUtil.java
 * Authors:             Justin Basilico
 * Company:             Sandia National Laboratories
 * Project:             Cognitive Foundry
 *
 * Copyright March 25, 2008, Sandia Corporation.
 * Under the terms of Contract DE-AC04-94AL85000, there is a non-exclusive
 * license for use of this work by or on behalf of the U.S. Government. Export
 * of this program may require a license from the United States Government.
 * See CopyrightHistory.txt for complete details.
 *
 */

import java.util.Collection;

import java.util.Iterator;

import java.util.List;

public class Main {
    /**
     * Gets the last element of the list. If the list is null or empty, null is
     * returned.
     *
     * @param <T> The type of element in the list.
     * @param list The list to get the last element from.
     * @return The last element from the list, if one exists. Otherwise, null.
     */
    public static <T> T getLast(final List<? extends T> list) {
        if (list == null || list.isEmpty()) {
            return null;
        } else {
            return list.get(list.size() - 1);
        }
    }

    /**
     * Returns true if the given collection is null or empty.
     *
     * @param collection The collection to determine if it is null or empty.
     * @return True if the given collection is null or empty.
     */
    public static boolean isEmpty(final Collection<?> collection) {
        return collection == null || collection.isEmpty();
    }

    /**
     * Returns true if the given iterable is null or empty.
     *
     * @param iterable The iterable to determine if it is null or empty.
     * @return True if the given iterable is null or empty.
     */
    public static boolean isEmpty(final Iterable<?> iterable) {
        if (iterable == null) {
            // It is null, so it is empty.
            return true;
        } else if (iterable instanceof Collection) {
            return ((Collection<?>) iterable).isEmpty();
        } else {
            return !iterable.iterator().hasNext();
        }
    }

    /**
     * Determines the size of the given collection, checking for null.
     *
     * @param collection The collection to get the size of.
     * @return The size of the collection. If it is null, zero is returned.
     */
    public static int size(final Collection<?> collection) {
        if (collection == null) {
            return 0;
        } else {
            return collection.size();
        }
    }

    /**
     * Determines the size of the given iterable. If it is null, zero is
     * returned. If it is a {@code Collection}, then the size method is used.
     * Otherwise, the iterable is iterated over to get the size.
     *
     * @param iterable The iterable to determine the size of.
     * @return The size of the given iterable.
     */
    public static int size(final Iterable<?> iterable) {
        if (iterable == null) {
            // The size is zero.
            return 0;
        } else if (iterable instanceof Collection) {
            // Get the size from the collection. This cast is justified by
            // not having to loop over all the elements.
            return ((Collection<?>) iterable).size();
        } else {
            // Cound up the elements in the iterable.
            int counter = 0;
            final Iterator<?> iterator = iterable.iterator();
            while (iterator.hasNext()) {
                iterator.next();
                counter++;
            }
            return counter;
        }
    }
}

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