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.list; 018 019import java.util.Collection; 020import java.util.Iterator; 021import java.util.List; 022import java.util.ListIterator; 023import java.util.function.Predicate; 024 025import org.apache.commons.collections4.BoundedCollection; 026import org.apache.commons.collections4.iterators.AbstractListIteratorDecorator; 027import org.apache.commons.collections4.iterators.UnmodifiableIterator; 028 029/** 030 * Decorates another {@code List} to fix the size preventing add/remove. 031 * <p> 032 * The add, remove, clear and retain operations are unsupported. 033 * The set method is allowed (as it doesn't change the list size). 034 * </p> 035 * <p> 036 * NOTE: 037 * Modifying the decorated list directly would results in influencing the outcome 038 * of method calls on this object. For example, the bounds of this list would reflect 039 * a newly added object to the underlying list. 040 * </p> 041 * <p> 042 * This class is Serializable from Commons Collections 3.1. 043 * </p> 044 * 045 * @param <E> the type of elements in this collection 046 * @since 3.0 047 */ 048public class FixedSizeList<E> 049 extends AbstractSerializableListDecorator<E> 050 implements BoundedCollection<E> { 051 052 /** 053 * List iterator that only permits changes via set() 054 */ 055 private final class FixedSizeListIterator extends AbstractListIteratorDecorator<E> { 056 protected FixedSizeListIterator(final ListIterator<E> iterator) { 057 super(iterator); 058 } 059 @Override 060 public void add(final Object object) { 061 throw unsupportedOperationException(); 062 } 063 @Override 064 public void remove() { 065 throw unsupportedOperationException(); 066 } 067 } 068 069 /** Serialization version */ 070 private static final long serialVersionUID = -2218010673611160319L; 071 072 /** 073 * Factory method to create a fixed size list. 074 * 075 * @param <E> the type of the elements in the list 076 * @param list the list to decorate, must not be null 077 * @return a new fixed size list 078 * @throws NullPointerException if list is null 079 * @since 4.0 080 */ 081 public static <E> FixedSizeList<E> fixedSizeList(final List<E> list) { 082 return new FixedSizeList<>(list); 083 } 084 085 private static UnsupportedOperationException unsupportedOperationException() { 086 return new UnsupportedOperationException("List is fixed size"); 087 } 088 089 /** 090 * Constructor that wraps (not copies). 091 * 092 * @param list the list to decorate, must not be null 093 * @throws NullPointerException if list is null 094 */ 095 protected FixedSizeList(final List<E> list) { 096 super(list); 097 } 098 099 @Override 100 public boolean add(final E object) { 101 throw unsupportedOperationException(); 102 } 103 104 @Override 105 public void add(final int index, final E object) { 106 throw unsupportedOperationException(); 107 } 108 109 @Override 110 public boolean addAll(final Collection<? extends E> coll) { 111 throw unsupportedOperationException(); 112 } 113 114 @Override 115 public boolean addAll(final int index, final Collection<? extends E> coll) { 116 throw unsupportedOperationException(); 117 } 118 119 @Override 120 public void clear() { 121 throw unsupportedOperationException(); 122 } 123 124 @Override 125 public E get(final int index) { 126 return decorated().get(index); 127 } 128 129 @Override 130 public int indexOf(final Object object) { 131 return decorated().indexOf(object); 132 } 133 134 @Override 135 public boolean isFull() { 136 return true; 137 } 138 139 @Override 140 public Iterator<E> iterator() { 141 return UnmodifiableIterator.unmodifiableIterator(decorated().iterator()); 142 } 143 144 @Override 145 public int lastIndexOf(final Object object) { 146 return decorated().lastIndexOf(object); 147 } 148 149 @Override 150 public ListIterator<E> listIterator() { 151 return new FixedSizeListIterator(decorated().listIterator(0)); 152 } 153 154 @Override 155 public ListIterator<E> listIterator(final int index) { 156 return new FixedSizeListIterator(decorated().listIterator(index)); 157 } 158 159 @Override 160 public int maxSize() { 161 return size(); 162 } 163 164 @Override 165 public E remove(final int index) { 166 throw unsupportedOperationException(); 167 } 168 169 @Override 170 public boolean remove(final Object object) { 171 throw unsupportedOperationException(); 172 } 173 174 @Override 175 public boolean removeAll(final Collection<?> coll) { 176 throw unsupportedOperationException(); 177 } 178 179 /** 180 * @since 4.4 181 */ 182 @Override 183 public boolean removeIf(final Predicate<? super E> filter) { 184 throw unsupportedOperationException(); 185 } 186 187 @Override 188 public boolean retainAll(final Collection<?> coll) { 189 throw unsupportedOperationException(); 190 } 191 192 @Override 193 public E set(final int index, final E object) { 194 return decorated().set(index, object); 195 } 196 197 @Override 198 public List<E> subList(final int fromIndex, final int toIndex) { 199 final List<E> sub = decorated().subList(fromIndex, toIndex); 200 return new FixedSizeList<>(sub); 201 } 202 203}