java.util.AbstractMap Maven / Gradle / Ivy
/*
* 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;
}
}