src/main/java/org/mockito/internal/util/collections/Iterables.java

/*
 * Copyright (c) 2016 Mockito contributors
 * This program is made available under the terms of the MIT License.
 */
package org.mockito.internal.util.collections;

import java.util.Enumeration;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

/**
 * Utilities for Iterables
 */
public class Iterables {

    /**
     * Converts enumeration into iterable
     */
    public static <T> Iterable<T> toIterable(Enumeration<T> in) {
        List<T> out = new LinkedList<T>();
        while(in.hasMoreElements()) {
            out.add(in.nextElement());
        }
        return out;
    }

    /**
     * Returns first element of provided iterable or fails fast when iterable is empty.
     *
     * @param iterable non-empty iterable
     * @return first element of supplied iterable
     * @throws IllegalArgumentException when supplied iterable is empty
     */
    public static <T> T firstOf(Iterable<T> iterable) {
        Iterator<T> iterator = iterable.iterator();
        if (!iterator.hasNext()) {
            throw new IllegalArgumentException("Cannot provide 1st element from empty iterable: " + iterable);
        }
        return iterator.next();
    }
}