Java tutorial
//package com.java2s; /* * Copyright 2002-2015 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 org.springframework.util.*; import java.util.Collection; import java.util.Map; public class Main { /** * Find a single value of the given type in the given Collection. * * @param collection the Collection to search * @param type the type to look for * @return a value of the given type found if there is a clear match, * or {@code null} if none or more than one such value found */ @SuppressWarnings("unchecked") public static <T> T findValueOfType(Collection<?> collection, Class<T> type) { if (isEmpty(collection)) { return null; } T value = null; for (Object element : collection) { if (type == null || type.isInstance(element)) { if (value != null) { // More than one value found... no clear single value. return null; } value = (T) element; } } return value; } /** * Find a single value of one of the given types in the given Collection: * searching the Collection for a value of the first type, then * searching for a value of the second type, etc. * * @param collection the collection to search * @param types the types to look for, in prioritized order * @return a value of one of the given types found if there is a clear match, * or {@code null} if none or more than one such value found */ public static Object findValueOfType(Collection<?> collection, Class<?>[] types) { if (isEmpty(collection) || ObjectUtils.isEmpty(types)) { return null; } for (Class<?> type : types) { Object value = findValueOfType(collection, type); if (value != null) { return value; } } return null; } /** * 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()); } }