Java Collection Element Get getElementFromSize1(Collection collection)

Description

get Element From Size

License

Apache License

Declaration

public static <T> T getElementFromSize1(Collection<T> collection) 

Method Source Code

//package com.java2s;
/* //from w  w  w  .jav  a 2  s  .c o  m
 * Copyright 2014 Topeka Labs.
 *
 * 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;

public class Main {
    public static <T> T getElementFromSize1(Collection<T> collection) {
        isNotSize1Exception(collection);
        return getSingleElement(collection);
    }

    public static void isNotSize1Exception(Collection collection, String collectionName) {
        if (collection.size() != 1) {
            throw new IllegalArgumentException(
                    "The size of " + collectionName + " is " + collection.size() + " when it should be 1");
        }
    }

    public static void isNotSize1Exception(Collection collection) {
        isNotSize1Exception(collection, "the collection");
    }

    public static <T> T getSingleElement(Collection<T> collection) {
        isEmptyException(collection);
        return collection.iterator().next();
    }

    /**
     * This method throws an IllegalArgumentException if the given collection
     * is empty.
     * @param collection The collection to check.
     */
    public static void isEmptyException(Collection collection) {
        if (collection.isEmpty()) {
            throw new IllegalArgumentException("The given collection cannot be empty.");
        }
    }

    /**
     * This method throws an IllegalArgumentException if the given collection is
     * empty. The name of the collection is included in the exception message.
     * @param collection The collection to check.
     * @param collectionName The name of the collection.
     */
    public static void isEmptyException(Collection collection, String collectionName) {
        if (collection.isEmpty()) {
            throw new IllegalArgumentException("The given collection " + collectionName + " cannot be empty.");
        }
    }
}

Related

1. getCommonSuffix(Collection c)
2. getComponentName(Collection existingNames, String name)
3. getDocIdString(Collection docIds)
4. getElement(final int index, final Collection coll)
5. getElementClass(Collection collection)
6. getEntropy(Collection values)
7. getEnumNames( Collection values)
8. getFlatString(Collection elements)
9. getGivenClassObject(Collection coll, Class clazz)