Find a single value of the given type in the given Collection. - Java java.util

Java examples for java.util:Collection Search

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Description

Find a single value of the given type in the given Collection.

Demo Code

/*/*  www  .  jav a 2  s  .c  om*/
 * 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.
 */
//package com.java2s;
import java.util.*;

public class Main {
    public static void main(String[] argv) {
        Collection collection = java.util.Arrays.asList("asdf",
                "java2s.com");
        Class type = String.class;
        System.out.println(findValueOfType(collection, type));
    }

    /**
     * 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)
                || org.springframework.util.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());
    }
}

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