Here you can find the source of treeSet(final T item)
public static <T> TreeSet<T> treeSet(final T item)
//package com.java2s; /*/*from ww w . j ava 2s . com*/ * Copyright 2016 Crown Copyright * * 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.TreeSet; public class Main { public static <T> TreeSet<T> treeSet(final T item) { final TreeSet<T> treeSet = new TreeSet<>(); if (null != item) { treeSet.add(item); } return treeSet; } public static <T> TreeSet<T> treeSet(final T[] items) { final TreeSet<T> treeSet = new TreeSet<>(); if (null != items) { for (final T item : items) { if (null != item) { treeSet.add(item); } } } return treeSet; } }