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/*
* 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;
/**
* This class is an abstract implementation of the {@code Map} interface. This
* implementation does not support adding. A subclass must implement the
* abstract method entrySet().
*
* @since 1.2
*/
public abstract class AbstractMap implements Map {
// Lazily initialized key set.
Set keySet;
Collection valuesCollection;
/**
* An immutable key-value mapping.
*
* @param
* the type of key
* @param
* the type of value
*
* @since 1.6
*/
public static class SimpleImmutableEntry implements Map.Entry {
private static final long serialVersionUID = 7138329143949025153L;
private K key;
private V value;
/**
* Constructs a new instance by key and value.
*
* @param theKey
* the key
* @param theValue
* the value
*/
public SimpleImmutableEntry(K theKey, V theValue) {
key = theKey;
value = theValue;
}
/**
* Constructs a new instance by an entry
*
* @param entry
* the entry
*/
public SimpleImmutableEntry(Map.Entry entry) {
key = entry.getKey();
value = entry.getValue();
}
/**
* {@inheritDoc}
*
* @see java.util.Map.Entry#getKey()
*/
public K getKey() {
return key;
}
/**
* {@inheritDoc}
*
* @see java.util.Map.Entry#getValue()
*/
public V getValue() {
return value;
}
/**
* Throws an UnsupportedOperationException.
*
* @param object
* new value
* @return (Does not)
* @throws UnsupportedOperationException
* always
*
* @see java.util.Map.Entry#setValue(java.lang.Object)
*/
public V setValue(@SuppressWarnings("unused")
V object) {
throw new UnsupportedOperationException();
}
/**
* Answers whether the object is equal to this entry. This works across
* all kinds of the Map.Entry interface.
*
* @see java.lang.Object#equals(java.lang.Object)
*/
@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;
}
/**
* Answers the hash code of this entry.
*
* @see java.lang.Object#hashCode()
*/
@Override
public int hashCode() {
return (key == null ? 0 : key.hashCode())
^ (value == null ? 0 : value.hashCode());
}
/**
* Answers a String representation of this entry.
*
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
return key + "=" + value; //$NON-NLS-1$
}
}
/**
* A key-value mapping.
*
* @param
* the type of key
* @param
* the type of value
*
* @since 1.6
*/
public static class SimpleEntry implements Map.Entry {
private static final long serialVersionUID = -8499721149061103585L;
private K key;
private V value;
/**
* Constructs a new instance by key and value.
*
* @param theKey
* the key
* @param theValue
* the value
*/
public SimpleEntry(K theKey, V theValue) {
key = theKey;
value = theValue;
}
/**
* Constructs a new instance by an entry
*
* @param entry
* the entry
*/
public SimpleEntry(Map.Entry entry) {
key = entry.getKey();
value = entry.getValue();
}
/**
* {@inheritDoc}
*
* @see java.util.Map.Entry#getKey()
*/
public K getKey() {
return key;
}
/**
* {@inheritDoc}
*
* @see java.util.Map.Entry#getValue()
*/
public V getValue() {
return value;
}
/**
* {@inheritDoc}
*
* @see java.util.Map.Entry#setValue(java.lang.Object)
*/
public V setValue(V object) {
V result = value;
value = object;
return result;
}
/**
* Answers whether the object is equal to this entry. This works across
* all kinds of the Map.Entry interface.
*
* @see java.lang.Object#equals(java.lang.Object)
*/
@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;
}
/**
* Answers the hash code of this entry.
*
* @see java.lang.Object#hashCode()
*/
@Override
public int hashCode() {
return (key == null ? 0 : key.hashCode())
^ (value == null ? 0 : value.hashCode());
}
/**
* Answers a String representation of this entry.
*
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
return key + "=" + value; //$NON-NLS-1$
}
}
/**
* Constructs a new instance of this {@code AbstractMap}.
*/
protected AbstractMap() {
super();
}
/**
* Removes all elements from this map, leaving it empty.
*
* @throws UnsupportedOperationException
* if removing from this map is not supported.
* @see #isEmpty()
* @see #size()
*/
public void clear() {
entrySet().clear();
}
/**
* Returns whether this map contains the specified key.
*
* @param key
* the key to search for.
* @return {@code true} if this map contains the specified key,
* {@code false} otherwise.
*/
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;
}
/**
* Returns whether this map contains the specified value.
*
* @param value
* the value to search for.
* @return {@code true} if this map contains the specified value,
* {@code false} otherwise.
*/
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;
}
/**
* Returns a set containing all of the mappings in this map. Each mapping is
* an instance of {@link Map.Entry}. As the set is backed by this map,
* changes in one will be reflected in the other.
*
* @return a set of the mappings.
*/
public abstract Set> entrySet();
/**
* Compares the specified object to this instance, and returns {@code true}
* if the specified object is a map and both maps contain the same mappings.
*
* @param object
* the object to compare with this object.
* @return boolean {@code true} if the object is the same as this object,
* and {@code false} if it is different from this object.
* @see #hashCode()
* @see #entrySet()
*/
@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 {
Iterator> it = entrySet().iterator();
while (it.hasNext()) {
Entry entry = it.next();
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;
}
/**
* Returns the value of the mapping with the specified key.
*
* @param key
* the key.
* @return the value of the mapping with the specified key, or {@code null}
* if no mapping for the specified key is found.
*/
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;
}
/**
* Returns the hash code for this object. Objects which are equal must
* return the same value for this method.
*
* @return the hash code of this object.
* @see #equals(Object)
*/
@Override
public int hashCode() {
int result = 0;
Iterator> it = entrySet().iterator();
while (it.hasNext()) {
result += it.next().hashCode();
}
return result;
}
/**
* Returns whether this map is empty.
*
* @return {@code true} if this map has no elements, {@code false}
* otherwise.
* @see #size()
*/
public boolean isEmpty() {
return size() == 0;
}
/**
* Returns a set of the keys contained in this map. The set is backed by
* this map so changes to one are reflected by the other. The returned set
* does not support adding.
*
* @return a set of the 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;
}
/**
* Maps the specified key to the specified value.
*
* @param key
* the key.
* @param value
* the value.
* @return the value of any previous mapping with the specified key or
* {@code null} if there was no mapping.
* @throws UnsupportedOperationException
* if adding to this map is not supported.
* @throws ClassCastException
* if the class of the key or value is inappropriate for this
* map.
* @throws IllegalArgumentException
* if the key or value cannot be added to this map.
* @throws NullPointerException
* if the key or value is {@code null} and this Map does not
* support {@code null} keys or values.
*/
public V put(@SuppressWarnings("unused")
K key, @SuppressWarnings("unused")
V value) {
throw new UnsupportedOperationException();
}
/**
* Copies every mapping in the specified map to this map.
*
* @param map
* the map to copy mappings from.
* @throws UnsupportedOperationException
* if adding to this map is not supported.
* @throws ClassCastException
* if the class of a key or value is inappropriate for this
* map.
* @throws IllegalArgumentException
* if a key or value cannot be added to this map.
* @throws NullPointerException
* if a key or value is {@code null} and this map does not
* support {@code null} keys or values.
*/
public void putAll(Map map) {
Iterator it = map.entrySet().iterator();
while (it.hasNext()) {
Map.Entry entry = (Map.Entry)it.next();
put(entry.getKey(), entry.getValue());
}
}
/**
* Removes a mapping with the specified key from this Map.
*
* @param key
* the key of the mapping to remove.
* @return the value of the removed mapping or {@code null} if no mapping
* for the specified key was found.
* @throws UnsupportedOperationException
* if removing from this map is not supported.
*/
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;
}
/**
* Returns the number of elements in this map.
*
* @return the number of elements in this map.
*/
public int size() {
return entrySet().size();
}
/**
* Returns the string representation of this map.
*
* @return the string representation of this map.
*/
@Override
public String toString() {
if (isEmpty()) {
return "{}"; //$NON-NLS-1$
}
StringBuffer buffer = new StringBuffer(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)"); //$NON-NLS-1$
}
buffer.append('=');
Object value = entry.getValue();
if (value != this) {
buffer.append(value);
} else {
buffer.append("(this Map)"); //$NON-NLS-1$
}
if (it.hasNext()) {
buffer.append(", "); //$NON-NLS-1$
}
}
buffer.append('}');
return buffer.toString();
}
/**
* Returns a collection of the values contained in this map. The collection
* is backed by this map so changes to one are reflected by the other. The
* collection supports remove, removeAll, retainAll and clear operations,
* and it does not support add or addAll operations.
*
* This method returns a collection which is the subclass of
* AbstractCollection. The iterator method of this subclass returns a
* "wrapper object" over the iterator of map's entrySet(). The {@code size}
* method wraps the map's size method and the {@code contains} method wraps
* the map's containsValue method.
*
* The collection is created when this method is called for the first time
* and returned in response to all subsequent calls. This method may return
* different collections when multiple concurrent calls occur to this
* method, since no synchronization is performed.
*
* @return a collection of the values contained in this map.
*/
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;
}
}