001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.collections4.collection; 018 019import java.util.Collection; 020import java.util.Iterator; 021import java.util.function.Predicate; 022 023import org.apache.commons.collections4.Unmodifiable; 024import org.apache.commons.collections4.iterators.UnmodifiableIterator; 025 026/** 027 * Decorates another {@link Collection} to ensure it can't be altered. 028 * <p> 029 * This class is Serializable from Commons Collections 3.1. 030 * </p> 031 * <p> 032 * Attempts to modify it will result in an UnsupportedOperationException. 033 * </p> 034 * 035 * @param <E> the type of the elements in the collection 036 * @since 3.0 037 */ 038public final class UnmodifiableCollection<E> 039 extends AbstractCollectionDecorator<E> 040 implements Unmodifiable { 041 042 /** Serialization version */ 043 private static final long serialVersionUID = -239892006883819945L; 044 045 /** 046 * Factory method to create an unmodifiable collection. 047 * <p> 048 * If the collection passed in is already unmodifiable, it is returned. 049 * 050 * @param <T> the type of the elements in the collection 051 * @param coll the collection to decorate, must not be null 052 * @return an unmodifiable collection 053 * @throws NullPointerException if collection is null 054 * @since 4.0 055 */ 056 public static <T> Collection<T> unmodifiableCollection(final Collection<? extends T> coll) { 057 if (coll instanceof Unmodifiable) { 058 @SuppressWarnings("unchecked") // safe to upcast 059 final Collection<T> tmpColl = (Collection<T>) coll; 060 return tmpColl; 061 } 062 return new UnmodifiableCollection<>(coll); 063 } 064 065 //----------------------------------------------------------------------- 066 /** 067 * Constructor that wraps (not copies). 068 * 069 * @param coll the collection to decorate, must not be null 070 * @throws NullPointerException if collection is null 071 */ 072 @SuppressWarnings("unchecked") // safe to upcast 073 private UnmodifiableCollection(final Collection<? extends E> coll) { 074 super((Collection<E>) coll); 075 } 076 077 //----------------------------------------------------------------------- 078 @Override 079 public Iterator<E> iterator() { 080 return UnmodifiableIterator.unmodifiableIterator(decorated().iterator()); 081 } 082 083 @Override 084 public boolean add(final E object) { 085 throw new UnsupportedOperationException(); 086 } 087 088 @Override 089 public boolean addAll(final Collection<? extends E> coll) { 090 throw new UnsupportedOperationException(); 091 } 092 093 @Override 094 public void clear() { 095 throw new UnsupportedOperationException(); 096 } 097 098 @Override 099 public boolean remove(final Object object) { 100 throw new UnsupportedOperationException(); 101 } 102 103 /** 104 * @since 4.4 105 */ 106 @Override 107 public boolean removeIf(final Predicate<? super E> filter) { 108 throw new UnsupportedOperationException(); 109 } 110 111 @Override 112 public boolean removeAll(final Collection<?> coll) { 113 throw new UnsupportedOperationException(); 114 } 115 116 @Override 117 public boolean retainAll(final Collection<?> coll) { 118 throw new UnsupportedOperationException(); 119 } 120 121}