All Downloads are FREE. Search and download functionalities are using the official Maven repository.

java.util.AbstractMap Maven / Gradle / Ivy

There is a newer version: 1.2.9
Show newest version
/*
 *  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 java.util;

import java.io.Serializable;

/**
 * A base class for {@code Map} implementations.
 *
 * 

Subclasses that permit new mappings to be added must override {@link * #put}. * *

The default implementations of many methods are inefficient for large * maps. For example in the default implementation, each call to {@link #get} * performs a linear iteration of the entry set. Subclasses should override such * methods to improve their performance. * * @since 1.2 */ public abstract class AbstractMap implements Map { // Lazily-initialized key set (for implementing {@link #keySet}). Set keySet; // Lazily-initialized values collection (for implementing {@link #values}). Collection valuesCollection; /** * An immutable key-value mapping. Despite the name, this class is non-final * and its subclasses may be mutable. * * @since 1.6 */ public static class SimpleImmutableEntry implements Map.Entry, Serializable { private static final long serialVersionUID = 7138329143949025153L; private final K key; private final V value; public SimpleImmutableEntry(K theKey, V theValue) { key = theKey; value = theValue; } /** * Constructs an instance with the key and value of {@code copyFrom}. */ public SimpleImmutableEntry(Map.Entry copyFrom) { key = copyFrom.getKey(); value = copyFrom.getValue(); } public K getKey() { return key; } public V getValue() { return value; } /** * This base implementation throws {@code UnsupportedOperationException} * always. */ public V setValue(V object) { throw new UnsupportedOperationException(); } @Override public boolean equals(Object object) { if (this == object) { return true; } if (object instanceof Map.Entry) { Map.Entry entry = (Map.Entry) object; return (key == null ? entry.getKey() == null : key.equals(entry .getKey())) && (value == null ? entry.getValue() == null : value .equals(entry.getValue())); } return false; } @Override public int hashCode() { return (key == null ? 0 : key.hashCode()) ^ (value == null ? 0 : value.hashCode()); } @Override public String toString() { return key + "=" + value; } } /** * A key-value mapping with mutable values. * * @since 1.6 */ public static class SimpleEntry implements Map.Entry, Serializable { private static final long serialVersionUID = -8499721149061103585L; private final K key; private V value; public SimpleEntry(K theKey, V theValue) { key = theKey; value = theValue; } /** * Constructs an instance with the key and value of {@code copyFrom}. */ public SimpleEntry(Map.Entry copyFrom) { key = copyFrom.getKey(); value = copyFrom.getValue(); } public K getKey() { return key; } public V getValue() { return value; } public V setValue(V object) { V result = value; value = object; return result; } @Override public boolean equals(Object object) { if (this == object) { return true; } if (object instanceof Map.Entry) { Map.Entry entry = (Map.Entry) object; return (key == null ? entry.getKey() == null : key.equals(entry .getKey())) && (value == null ? entry.getValue() == null : value .equals(entry.getValue())); } return false; } @Override public int hashCode() { return (key == null ? 0 : key.hashCode()) ^ (value == null ? 0 : value.hashCode()); } @Override public String toString() { return key + "=" + value; } } protected AbstractMap() { } /** * {@inheritDoc} * *

This implementation calls {@code entrySet().clear()}. */ public void clear() { entrySet().clear(); } /** * {@inheritDoc} * *

This implementation iterates its key set, looking for a key that * {@code key} equals. */ public boolean containsKey(Object key) { Iterator> it = entrySet().iterator(); if (key != null) { while (it.hasNext()) { if (key.equals(it.next().getKey())) { return true; } } } else { while (it.hasNext()) { if (it.next().getKey() == null) { return true; } } } return false; } /** * {@inheritDoc} * *

This implementation iterates its entry set, looking for an entry with * a value that {@code value} equals. */ public boolean containsValue(Object value) { Iterator> it = entrySet().iterator(); if (value != null) { while (it.hasNext()) { if (value.equals(it.next().getValue())) { return true; } } } else { while (it.hasNext()) { if (it.next().getValue() == null) { return true; } } } return false; } public abstract Set> entrySet(); /** * {@inheritDoc} * *

This implementation first checks the structure of {@code object}. If * it is not a map or of a different size, this returns false. Otherwise it * iterates its own entry set, looking up each entry's key in {@code * object}. If any value does not equal the other map's value for the same * key, this returns false. Otherwise it returns true. */ @Override public boolean equals(Object object) { if (this == object) { return true; } if (object instanceof Map) { Map map = (Map) object; if (size() != map.size()) { return false; } try { for (Entry entry : entrySet()) { K key = entry.getKey(); V mine = entry.getValue(); Object theirs = map.get(key); if (mine == null) { if (theirs != null || !map.containsKey(key)) { return false; } } else if (!mine.equals(theirs)) { return false; } } } catch (NullPointerException ignored) { return false; } catch (ClassCastException ignored) { return false; } return true; } return false; } /** * {@inheritDoc} * *

This implementation iterates its entry set, looking for an entry with * a key that {@code key} equals. */ public V get(Object key) { Iterator> it = entrySet().iterator(); if (key != null) { while (it.hasNext()) { Map.Entry entry = it.next(); if (key.equals(entry.getKey())) { return entry.getValue(); } } } else { while (it.hasNext()) { Map.Entry entry = it.next(); if (entry.getKey() == null) { return entry.getValue(); } } } return null; } /** * {@inheritDoc} * *

This implementation iterates its entry set, summing the hashcodes of * its entries. */ @Override public int hashCode() { int result = 0; Iterator> it = entrySet().iterator(); while (it.hasNext()) { result += it.next().hashCode(); } return result; } /** * {@inheritDoc} * *

This implementation compares {@code size()} to 0. */ public boolean isEmpty() { return size() == 0; } /** * {@inheritDoc} * *

This implementation returns a view that calls through this to map. Its * iterator transforms this map's entry set iterator to return keys. */ public Set keySet() { if (keySet == null) { keySet = new AbstractSet() { @Override public boolean contains(Object object) { return containsKey(object); } @Override public int size() { return AbstractMap.this.size(); } @Override public Iterator iterator() { return new Iterator() { Iterator> setIterator = entrySet().iterator(); public boolean hasNext() { return setIterator.hasNext(); } public K next() { return setIterator.next().getKey(); } public void remove() { setIterator.remove(); } }; } }; } return keySet; } /** * {@inheritDoc} * *

This base implementation throws {@code UnsupportedOperationException}. */ public V put(K key, V value) { throw new UnsupportedOperationException(); } /** * {@inheritDoc} * *

This implementation iterates through {@code map}'s entry set, calling * {@code put()} for each. */ public void putAll(Map map) { for (Map.Entry entry : map.entrySet()) { put(entry.getKey(), entry.getValue()); } } /** * {@inheritDoc} * *

This implementation iterates its entry set, removing the entry with * a key that {@code key} equals. */ public V remove(Object key) { Iterator> it = entrySet().iterator(); if (key != null) { while (it.hasNext()) { Map.Entry entry = it.next(); if (key.equals(entry.getKey())) { it.remove(); return entry.getValue(); } } } else { while (it.hasNext()) { Map.Entry entry = it.next(); if (entry.getKey() == null) { it.remove(); return entry.getValue(); } } } return null; } /** * {@inheritDoc} * *

This implementation returns its entry set's size. */ public int size() { return entrySet().size(); } /** * {@inheritDoc} * *

This implementation composes a string by iterating its entry set. If * this map contains itself as a key or a value, the string "(this Map)" * will appear in its place. */ @Override public String toString() { if (isEmpty()) { return "{}"; } StringBuilder buffer = new StringBuilder(size() * 28); buffer.append('{'); Iterator> it = entrySet().iterator(); while (it.hasNext()) { Map.Entry entry = it.next(); Object key = entry.getKey(); if (key != this) { buffer.append(key); } else { buffer.append("(this Map)"); } buffer.append('='); Object value = entry.getValue(); if (value != this) { buffer.append(value); } else { buffer.append("(this Map)"); } if (it.hasNext()) { buffer.append(", "); } } buffer.append('}'); return buffer.toString(); } /** * {@inheritDoc} * *

This implementation returns a view that calls through this to map. Its * iterator transforms this map's entry set iterator to return values. */ public Collection values() { if (valuesCollection == null) { valuesCollection = new AbstractCollection() { @Override public int size() { return AbstractMap.this.size(); } @Override public boolean contains(Object object) { return containsValue(object); } @Override public Iterator iterator() { return new Iterator() { Iterator> setIterator = entrySet().iterator(); public boolean hasNext() { return setIterator.hasNext(); } public V next() { return setIterator.next().getValue(); } public void remove() { setIterator.remove(); } }; } }; } return valuesCollection; } @SuppressWarnings("unchecked") @Override protected Object clone() throws CloneNotSupportedException { AbstractMap result = (AbstractMap) super.clone(); result.keySet = null; result.valuesCollection = null; return result; } }





© 2015 - 2024 Weber Informatics LLC | Privacy Policy