Checks if the specified collection/array/iterator is empty. - Java Collection Framework

Java examples for Collection Framework:Array Element

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Description

Checks if the specified collection/array/iterator is empty.

Demo Code


//package com.java2s;
import java.lang.reflect.Array;

import java.util.Collection;

import java.util.Enumeration;

import java.util.Iterator;

import java.util.Map;

public class Main {
    public static void main(String[] argv) {
        Object object = "java2s.com";
        System.out.println(sizeIsEmpty(object));
    }/*from   w ww. jav a2  s  .  com*/

    /**
     * Checks if the specified collection/array/iterator is empty.
     * <p>
     * This method can handles objects as follows
     * <ul>
     * <li>Collection - via collection isEmpty
     * <li>Map - via map isEmpty
     * <li>Array - using array size
     * <li>Iterator - via hasNext
     * <li>Enumeration - via hasMoreElements
     * </ul>
     * <p>
     * Note: This method is named to avoid clashing with
     * {@link #isEmpty(Collection)}.
     * 
     * @param object
     *            the object to get the size of, not null
     * @return true if empty
     * @throws IllegalArgumentException
     *             thrown if object is not recognised or null
     */
    public static boolean sizeIsEmpty(Object object) {
        if (object instanceof Collection) {
            return ((Collection<?>) object).isEmpty();
        } else if (object instanceof Map) {
            return ((Map<?, ?>) object).isEmpty();
        } else if (object instanceof Object[]) {
            return ((Object[]) object).length == 0;
        } else if (object instanceof Iterator) {
            return !((Iterator<?>) object).hasNext();
        } else if (object instanceof Enumeration) {
            return !((Enumeration<?>) object).hasMoreElements();
        } else if (object == null) {
            throw new IllegalArgumentException(
                    "Unsupported object type: null");
        } else {
            try {
                return Array.getLength(object) == 0;
            } catch (IllegalArgumentException ex) {
                throw new IllegalArgumentException(
                        "Unsupported object type: "
                                + object.getClass().getName());
            }
        }
    }

}

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