Android Collection Duplicate Remove hasUniqueObject(Collection collection)

Description

Determine whether the given Collection only contains a single unique object.

License

Apache License

Parameter

Parameter	Description
collection	the Collection to check

Return

true if the collection contains a single reference or multiple references to the same instance, false else

Declaration

public static boolean hasUniqueObject(Collection<?> collection) 

Method Source Code

//package com.java2s;
/*/* w w  w.  j a  v  a 2  s.c  o m*/
 * Copyright 2002-2013 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.util.Collection;

import java.util.Map;

public class Main {
    /**
     * Determine whether the given Collection only contains a single unique
     * object.
     * 
     * @param collection
     *            the Collection to check
     * @return <code>true</code> if the collection contains a single reference
     *         or multiple references to the same instance, <code>false</code>
     *         else
     */
    public static boolean hasUniqueObject(Collection<?> collection) {
        if (isEmpty(collection)) {
            return false;
        }
        boolean hasCandidate = false;
        Object candidate = null;
        for (Object elem : collection) {
            if (!hasCandidate) {
                hasCandidate = true;
                candidate = elem;
            } else if (candidate != elem) {
                return false;
            }
        }
        return true;
    }

    /**
     * Return <code>true</code> if the supplied Collection is <code>null</code>
     * or empty. Otherwise, return <code>false</code>.
     * 
     * @param collection
     *            the Collection to check
     * @return whether the given Collection is empty
     */
    public static boolean isEmpty(Collection<?> collection) {
        return (collection == null || collection.isEmpty());
    }

    /**
     * Return <code>true</code> if the supplied Map is <code>null</code> or
     * empty. Otherwise, return <code>false</code>.
     * 
     * @param map
     *            the Map to check
     * @return whether the given Map is empty
     */
    public static boolean isEmpty(Map<?, ?> map) {
        return (map == null || map.isEmpty());
    }
}

Related

1. hasUniqueObject(Collection collection)