Here you can find the source of getFirst(Collection
public static <T> T getFirst(Collection<T> c)
//package com.java2s; /*/* w w w.ja v a 2s . c o m*/ * Copyright (c) 2013, SRI International * All rights reserved. * Licensed under the The BSD 3-Clause License; * you may not use this file except in compliance with the License. * You may obtain a copy of the License at: * * http://opensource.org/licenses/BSD-3-Clause * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * Neither the name of the aic-util nor the names of its * contributors may be used to endorse or promote products derived from * this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED * OF THE POSSIBILITY OF SUCH DAMAGE. */ import java.util.Arrays; import java.util.Collection; import java.util.Iterator; public class Main { public static <T> T getFirst(Iterator<T> i) { return i.next(); } public static <T> T getFirst(Collection<T> c) { return getFirst(c.iterator()); } /** * Construct an iterator of the given type ranging over provided elements. * * @param elements * the elements to construct the List from. * @return an iterator over the received arguments. * @param <T> * the type of elements the iterator will range over. */ public static <T> Iterator<T> iterator(T... elements) { return Arrays.asList(elements).iterator(); } }