Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.lang.reflect.Array;

import java.util.Collection;

import java.util.Enumeration;

import java.util.Iterator;

import java.util.Map;

public class Main {
    /**
     * Extract the lone element of the specified Collection.
     * @param <E> collection type
     * @param collection to read
     * @return sole member of collection
     * @throws IllegalArgumentException if collection is null/empty or contains more than one element
     * @since 4.0
     */
    public static <E> E extractSingleton(final Collection<E> collection) {
        if (collection == null || collection.size() != 1) {
            throw new IllegalArgumentException("Can extract singleton only when collection size == 1");
        }
        return collection.iterator().next();
    }

    /**
     * Gets the size of the collection/iterator specified.
     * <p>
     * This method can handles objects as follows
     * <ul>
     * <li>Collection - the collection size
     * <li>Map - the map size
     * <li>Array - the array size
     * <li>Iterator - the number of elements remaining in the iterator
     * <li>Enumeration - the number of elements remaining in the enumeration
     * </ul>
     *
     * @param object  the object to get the size of, may be null
     * @return the size of the specified collection or 0 if the object was null
     * @throws IllegalArgumentException thrown if object is not recognised
     * @since 3.1
     */
    public static int size(final Object object) {
        if (object == null) {
            return 0;
        }
        int total = 0;
        if (object instanceof Map<?, ?>) {
            total = ((Map<?, ?>) object).size();
        } else if (object instanceof Collection<?>) {
            total = ((Collection<?>) object).size();
        } else if (object instanceof Object[]) {
            total = ((Object[]) object).length;
        } else if (object instanceof Iterator<?>) {
            final Iterator<?> it = (Iterator<?>) object;
            while (it.hasNext()) {
                total++;
                it.next();
            }
        } else if (object instanceof Enumeration<?>) {
            final Enumeration<?> it = (Enumeration<?>) object;
            while (it.hasMoreElements()) {
                total++;
                it.nextElement();
            }
        } else {
            try {
                total = Array.getLength(object);
            } catch (final IllegalArgumentException ex) {
                throw new IllegalArgumentException("Unsupported object type: " + object.getClass().getName());
            }
        }
        return total;
    }
}