Java Collection Find findCommonElementType(Collection collection)

Description

Find the common element type of the given Collection, if any.

License

Apache License

Parameter

Parameter	Description
collection	the Collection to check

Return

the common element type, or null if no clear common type has been found (or the collection was empty)

Declaration

public static Class<?> findCommonElementType(Collection<?> collection) 

Method Source Code

//package com.java2s;
/*/*from w  w w  . ja v a  2 s  .  co  m*/
 * Copyright 2002-2014 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.*;

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} 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;
    }

    public static boolean isEmpty(Collection<?> collection) {
        return (collection == null || collection.isEmpty());
    }
}

Related

1. findClass(String name, Collection availableImports, ClassLoader cl)
2. findCommonElementType(Collection collection)
3. findCommonElementType(Collection collection)
4. findCommonElementType(Collection collection)
5. findMax(Collection vals)
6. findMax(Collection vals)
7. findMax(Iterable collection)