Here you can find the source of findCommonElementType(Collection> collection)
Parameter | Description |
---|---|
collection | the Collection to check |
null
if no clear common type has been found (or the collection was empty)
public static Class<?> findCommonElementType(Collection<?> collection)
//package com.java2s; /*//from w w w. j ava2 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 { /** * Find the common element type of the given Collection, if any. * * @param collection * the Collection to check * @return the common element type, or <code>null</code> if no clear common * type has been found (or the collection was empty) */ public static Class<?> findCommonElementType(Collection<?> collection) { if (isEmpty(collection)) { return null; } Class<?> candidate = null; for (Object val : collection) { if (val != null) { if (candidate == null) { candidate = val.getClass(); } else if (candidate != val.getClass()) { return null; } } } return candidate; } /** * 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()); } }