Here you can find the source of singleOrNull(Iterable
| Parameter | Description |
|---|---|
| iterable | any class implementing Iterable<T> interface |
| T | class of iterable element |
| Parameter | Description |
|---|---|
| IllegalArgumentException | If null is passed as an argument. |
| IllegalStateException | If iterable contains more than one element. |
public static <T> T singleOrNull(Iterable<T> iterable)
//package com.java2s; /*/*ww w.j a va 2 s . c om*/ * Copyright (c) 2015 Intel Corporation * * 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.Iterator; public class Main { /** * Method returns the single element from an iterable or null if empty iterable is passed. * * @param iterable any class implementing Iterable<T> interface * @param <T> class of iterable element * @return single object of class T or null * * @throws IllegalArgumentException * If null is passed as an argument. * * @throws IllegalStateException * If iterable contains more than one element. */ public static <T> T singleOrNull(Iterable<T> iterable) { if (iterable == null) { throw new IllegalArgumentException("Null is not a valid argument for this method"); } Iterator<T> iterator = iterable.iterator(); if (!iterable.iterator().hasNext()) { return null; } else { T element = iterator.next(); if (iterator.hasNext()) { throw new IllegalStateException("Only iterators with 1 or 0 elements are accepted!"); } return element; } } }