Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */ package org.apache.commons.collections4.map; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.Serializable; import java.util.Iterator; import java.util.Map; import org.apache.commons.collections4.Predicate; /** * Decorates another <code>Map</code> to validate that additions * match a specified predicate. * <p> * This map exists to provide validation for the decorated map. * It is normally created to decorate an empty map. * If an object cannot be added to the map, an IllegalArgumentException is thrown. * <p> * One usage would be to ensure that no null keys are added to the map. * <pre>Map map = PredicatedSet.decorate(new HashMap(), NotNullPredicate.INSTANCE, null);</pre> * <p> * <strong>Note that PredicatedMap is not synchronized and is not thread-safe.</strong> * If you wish to use this map from multiple threads concurrently, you must use * appropriate synchronization. The simplest approach is to wrap this map * using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw * exceptions when accessed by concurrent threads without synchronization. * <p> * This class is Serializable from Commons Collections 3.1. * * @since 3.0 * @version $Id: PredicatedMap.java 1479407 2013-05-05 22:07:53Z tn $ */ public class PredicatedMap<K, V> extends AbstractInputCheckedMapDecorator<K, V> implements Serializable { /** Serialization version */ private static final long serialVersionUID = 7412622456128415156L; /** The key predicate to use */ protected final Predicate<? super K> keyPredicate; /** The value predicate to use */ protected final Predicate<? super V> valuePredicate; /** * Factory method to create a predicated (validating) map. * <p> * If there are any elements already in the list being decorated, they * are validated. * * @param <K> the key type * @param <V> the value type * @param map the map to decorate, must not be null * @param keyPredicate the predicate to validate the keys, null means no check * @param valuePredicate the predicate to validate to values, null means no check * @return a new predicated map * @throws IllegalArgumentException if the map is null * @since 4.0 */ public static <K, V> PredicatedMap<K, V> predicatedMap(final Map<K, V> map, final Predicate<? super K> keyPredicate, final Predicate<? super V> valuePredicate) { return new PredicatedMap<K, V>(map, keyPredicate, valuePredicate); } //----------------------------------------------------------------------- /** * Constructor that wraps (not copies). * * @param map the map to decorate, must not be null * @param keyPredicate the predicate to validate the keys, null means no check * @param valuePredicate the predicate to validate to values, null means no check * @throws IllegalArgumentException if the map is null */ protected PredicatedMap(final Map<K, V> map, final Predicate<? super K> keyPredicate, final Predicate<? super V> valuePredicate) { super(map); this.keyPredicate = keyPredicate; this.valuePredicate = valuePredicate; final Iterator<Map.Entry<K, V>> it = map.entrySet().iterator(); while (it.hasNext()) { final Map.Entry<K, V> entry = it.next(); validate(entry.getKey(), entry.getValue()); } } //----------------------------------------------------------------------- /** * Write the map out using a custom routine. * * @param out the output stream * @throws IOException * @since 3.1 */ private void writeObject(final ObjectOutputStream out) throws IOException { out.defaultWriteObject(); out.writeObject(map); } /** * Read the map in using a custom routine. * * @param in the input stream * @throws IOException * @throws ClassNotFoundException * @since 3.1 */ @SuppressWarnings("unchecked") // (1) should only fail if input stream is incorrect private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException { in.defaultReadObject(); map = (Map<K, V>) in.readObject(); // (1) } //----------------------------------------------------------------------- /** * Validates a key value pair. * * @param key the key to validate * @param value the value to validate * @throws IllegalArgumentException if invalid */ protected void validate(final K key, final V value) { if (keyPredicate != null && keyPredicate.evaluate(key) == false) { throw new IllegalArgumentException("Cannot add key - Predicate rejected it"); } if (valuePredicate != null && valuePredicate.evaluate(value) == false) { throw new IllegalArgumentException("Cannot add value - Predicate rejected it"); } } /** * Override to validate an object set into the map via <code>setValue</code>. * * @param value the value to validate * @return the value itself * @throws IllegalArgumentException if invalid * @since 3.1 */ @Override protected V checkSetValue(final V value) { if (valuePredicate.evaluate(value) == false) { throw new IllegalArgumentException("Cannot set value - Predicate rejected it"); } return value; } /** * Override to only return true when there is a value transformer. * * @return true if a value predicate is in use * @since 3.1 */ @Override protected boolean isSetValueChecking() { return valuePredicate != null; } //----------------------------------------------------------------------- @Override public V put(final K key, final V value) { validate(key, value); return map.put(key, value); } @Override public void putAll(final Map<? extends K, ? extends V> mapToCopy) { for (final Map.Entry<? extends K, ? extends V> entry : mapToCopy.entrySet()) { validate(entry.getKey(), entry.getValue()); } super.putAll(mapToCopy); } }