Java List Last Item removeBySwapLast(List a, Object o)

Description

Removes element from List by swapping with last element.

License

GNU General Public License

Return

true if element was removed.

Declaration

public static <E> boolean removeBySwapLast(List<E> a, Object o) 

Method Source Code

//package com.java2s;
/* This code is part of Freenet. It is distributed under the GNU General
 * Public License, version 2 (or at your option any later version). See
 * http://www.gnu.org/ for further details of the GPL. */

import java.util.List;

public class Main {
    /**/*  ww  w  .  j  a  v  a  2 s .c o  m*/
     * Removes element from List by swapping with last element.
     * O(n) comparison, O(1) moves.
     * This method is useful with ArrayList-alike containers
     * with O(1) get(index) and O(n) remove(index)
     * when keeping array order is not important.
     * Not synchronized (even with synchronized containers).
     * @return {@code true} if element was removed.
     */
    public static <E> boolean removeBySwapLast(List<E> a, Object o) {
        int idx = a.indexOf(o);
        if (idx == -1)
            return false;
        removeBySwapLast(a, idx);
        return true;
    }

    /**
     * Removes element by index from List by swapping with last element.
     * 0 comparison, O(1) moves.
     * This method is useful with ArrayList-alike containers
     * with O(1) get(index) and O(n) remove(index)
     * when keeping array order is not important.
     * Not synchronized (even with synchronized containers!).
     * @return moved element that will replace current index or
     * removed element if it was last element (and nothing was moved).
     * WARNING: returned result is DIFFERENT from List.remove(index)!
     * (this is intentional to allow useful optimizations).
     * @throws IndexOutOfBoundsException if idx is not valid index
     * WARNING: Don't dare to break this method contract!
     */
    public static <E> E removeBySwapLast(List<E> a, int idx) {
        int size = a.size();
        if (idx < 0 || idx >= size)
            throw new IndexOutOfBoundsException(idx + " out of range [0;" + size + ")");
        E moved = a.remove(size - 1);
        if (idx != size - 1)
            a.set(idx, moved);
        return moved;
    }
}

Related

1. isLastIndex(List list, int index)
2. isLastIndex(List suggestedList, int i)
3. lastIndexOf(List lines, String... conditions)
4. lastIndexOfIdentical(List l, T element, int startingAt)
5. listToWorkspaceLocationHistoryString(List lastUsedWorkspaceLocationList)
6. removeLast(List list)
7. removeLast(List aList)
8. removeLast(List l)
9. removeLast(List list)