Java tutorial
//package com.java2s; /* * Copyright 2002-2008 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.Iterator; import java.util.Map; public class Main { public static boolean hasUniqueObject(Collection<?> collection) { if (isEmpty(collection)) { return false; } boolean hasCandidate = false; Object candidate = null; for (Iterator<?> it = collection.iterator(); it.hasNext();) { Object elem = it.next(); if (!hasCandidate) { hasCandidate = true; candidate = elem; } else if (candidate != elem) { return false; } } return true; } public static boolean isEmpty(Collection<?> collection) { return (collection == null || collection.isEmpty()); } public static boolean isEmpty(Map<?, ?> map) { return (map == null || map.isEmpty()); } }