Java Collection Search indexOfInstance(final Collection<? extends T> collection, final T instance)

Description

Determine the index position of the first occurrence of the given object instance in the given collection.

License

Open Source License

Parameter

Parameter	Description
collection	collection to check for contained instance
instance	specific object instance to check for
T	type of the object to check for

Return

position of the given instance in the collection (not just of an equal object)

Declaration

public static <T> int indexOfInstance(final Collection<? extends T> collection, final T instance)

Method Source Code

//package com.java2s;
/*//from  ww w  .  j av a  2 s .  com
   Copyright (C) 2016 HermeneutiX.org
    
   This file is part of SciToS.
    
   SciToS is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
    
   SciToS is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
    
   You should have received a copy of the GNU General Public License
   along with SciToS. If not, see <http://www.gnu.org/licenses/>.
 */

import java.util.Collection;

public class Main {
    /**
     * Determine the index position of the first occurrence of the given object instance in the given collection. Thereby avoiding the use of
     * {@link Object#equals(Object) equals(Object)} and {@link Object#hashCode() hashCode()} in the {@link java.util.List#indexOf(Object)
     * indexOf(Object)} implementation of the collection/list itself.
     *
     * <p>
     * This check is supposed to be faster and can be used with objects, that are missing proper implementations of those methods. Additionally,
     * objects that are deemed {@link Object#equals(Object) equal} but not identical are ignored.
     * </p>
     *
     * @param collection
     *            collection to check for contained instance
     * @param instance
     *            specific object instance to check for
     * @param <T>
     *            type of the object to check for
     * @return position of the given instance in the collection (not just of an equal object)
     */
    public static <T> int indexOfInstance(final Collection<? extends T> collection, final T instance) {
        if (collection != null && !collection.isEmpty()) {
            int index = 0;
            for (final T collectionElement : collection) {
                if (collectionElement == instance) {
                    return index;
                }
                index++;
            }
        }
        return -1;
    }
}

Java Collection Search indexOfInstance(final Collection collection, final T instance)