Java tutorial
//package com.java2s; /* * Copyright 2015, The Querydsl Team (http://www.querydsl.com/team) * * 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.List; import java.util.Set; import com.google.common.collect.*; public class Main { public static <T> Set<T> addSorted(Set<T> set, T element) { final int size = set.size(); if (size == 0) { return ImmutableSet.of(element); } else if (set instanceof ImmutableSet) { if (size == 1) { final T val = set.iterator().next(); set = Sets.newLinkedHashSet(); set.add(val); } else { set = Sets.newLinkedHashSet(set); } } set.add(element); return set; } public static <T> List<T> add(List<T> list, T element) { final int size = list.size(); if (size == 0) { return ImmutableList.of(element); } else if (list instanceof ImmutableList) { if (size == 1) { final T val = list.get(0); list = Lists.newArrayList(); list.add(val); } else { list = Lists.newArrayList(list); } } list.add(element); return list; } public static <T> Set<T> add(Set<T> set, T element) { final int size = set.size(); if (size == 0) { return ImmutableSet.of(element); } else if (set instanceof ImmutableSet) { if (size == 1) { final T val = set.iterator().next(); set = Sets.newHashSet(); set.add(val); } else { set = Sets.newHashSet(set); } } set.add(element); return set; } }