Java tutorial
//package com.java2s; /** * Copyright (C) 2014-2017 Philip Helger (www.helger.com) * philip[at]helger[dot]com * * 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; import java.util.List; import java.util.Map; import javax.annotation.Nullable; public class Main { @Nullable public static <ELEMENTTYPE> ELEMENTTYPE removeFirstElement(@Nullable final List<ELEMENTTYPE> aList) { return isEmpty(aList) ? null : aList.remove(0); } public static boolean isEmpty(@Nullable final Iterable<?> aCont) { return aCont == null || !aCont.iterator().hasNext(); } public static boolean isEmpty(@Nullable final Collection<?> aCont) { return aCont == null || aCont.isEmpty(); } public static boolean isEmpty(@Nullable final Map<?, ?> aCont) { return aCont == null || aCont.isEmpty(); } }