Java Collection Unique hasUniqueObject(Collection collection)

Description

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

License

Open Source 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;
//License from project: Open Source License 

import java.util.*;

public class Main {
    /**/*from  ww w  .  j  a v  a2s .  c  o m*/
     * Determine whether the given Collection only contains a single unique object.
     *
     * @param collection the Collection to check
     * @return {@code true} if the collection contains a single reference or
     * multiple references to the same instance, {@code false} 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} if the supplied Collection is {@code null}
     * or empty. Otherwise, return {@code false}.
     *
     * @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} if the supplied Map is {@code null}
     * or empty. Otherwise, return {@code false}.
     *
     * @param map the Map to check
     * @return whether the given Map is empty
     */
    public static boolean isEmpty(Map map) {
        return (map == null || map.isEmpty());
    }
}