| /* |
| * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.util; |
| import java.util.Map.Entry; |
| |
| /** |
| * This class provides a skeletal implementation of the <tt>Map</tt> |
| * interface, to minimize the effort required to implement this interface. |
| * |
| * <p>To implement an unmodifiable map, the programmer needs only to extend this |
| * class and provide an implementation for the <tt>entrySet</tt> method, which |
| * returns a set-view of the map's mappings. Typically, the returned set |
| * will, in turn, be implemented atop <tt>AbstractSet</tt>. This set should |
| * not support the <tt>add</tt> or <tt>remove</tt> methods, and its iterator |
| * should not support the <tt>remove</tt> method. |
| * |
| * <p>To implement a modifiable map, the programmer must additionally override |
| * this class's <tt>put</tt> method (which otherwise throws an |
| * <tt>UnsupportedOperationException</tt>), and the iterator returned by |
| * <tt>entrySet().iterator()</tt> must additionally implement its |
| * <tt>remove</tt> method. |
| * |
| * <p>The programmer should generally provide a void (no argument) and map |
| * constructor, as per the recommendation in the <tt>Map</tt> interface |
| * specification. |
| * |
| * <p>The documentation for each non-abstract method in this class describes its |
| * implementation in detail. Each of these methods may be overridden if the |
| * map being implemented admits a more efficient implementation. |
| * |
| * <p>This class is a member of the |
| * <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
| * Java Collections Framework</a>. |
| * |
| * @param <K> the type of keys maintained by this map |
| * @param <V> the type of mapped values |
| * |
| * @author Josh Bloch |
| * @author Neal Gafter |
| * @see Map |
| * @see Collection |
| * @since 1.2 |
| */ |
| |
| public abstract class AbstractMap<K,V> implements Map<K,V> { |
| /** |
| * Sole constructor. (For invocation by subclass constructors, typically |
| * implicit.) |
| */ |
| protected AbstractMap() { |
| } |
| |
| // Query Operations |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @implSpec |
| * This implementation returns <tt>entrySet().size()</tt>. |
| */ |
| public int size() { |
| return entrySet().size(); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @implSpec |
| * This implementation returns <tt>size() == 0</tt>. |
| */ |
| public boolean isEmpty() { |
| return size() == 0; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @implSpec |
| * This implementation iterates over <tt>entrySet()</tt> searching |
| * for an entry with the specified value. If such an entry is found, |
| * <tt>true</tt> is returned. If the iteration terminates without |
| * finding such an entry, <tt>false</tt> is returned. Note that this |
| * implementation requires linear time in the size of the map. |
| * |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| */ |
| public boolean containsValue(Object value) { |
| Iterator<Entry<K,V>> i = entrySet().iterator(); |
| if (value==null) { |
| while (i.hasNext()) { |
| Entry<K,V> e = i.next(); |
| if (e.getValue()==null) |
| return true; |
| } |
| } else { |
| while (i.hasNext()) { |
| Entry<K,V> e = i.next(); |
| if (value.equals(e.getValue())) |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @implSpec |
| * This implementation iterates over <tt>entrySet()</tt> searching |
| * for an entry with the specified key. If such an entry is found, |
| * <tt>true</tt> is returned. If the iteration terminates without |
| * finding such an entry, <tt>false</tt> is returned. Note that this |
| * implementation requires linear time in the size of the map; many |
| * implementations will override this method. |
| * |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| */ |
| public boolean containsKey(Object key) { |
| Iterator<Map.Entry<K,V>> i = entrySet().iterator(); |
| if (key==null) { |
| while (i.hasNext()) { |
| Entry<K,V> e = i.next(); |
| if (e.getKey()==null) |
| return true; |
| } |
| } else { |
| while (i.hasNext()) { |
| Entry<K,V> e = i.next(); |
| if (key.equals(e.getKey())) |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @implSpec |
| * This implementation iterates over <tt>entrySet()</tt> searching |
| * for an entry with the specified key. If such an entry is found, |
| * the entry's value is returned. If the iteration terminates without |
| * finding such an entry, <tt>null</tt> is returned. Note that this |
| * implementation requires linear time in the size of the map; many |
| * implementations will override this method. |
| * |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| */ |
| public V get(Object key) { |
| Iterator<Entry<K,V>> i = entrySet().iterator(); |
| if (key==null) { |
| while (i.hasNext()) { |
| Entry<K,V> e = i.next(); |
| if (e.getKey()==null) |
| return e.getValue(); |
| } |
| } else { |
| while (i.hasNext()) { |
| Entry<K,V> e = i.next(); |
| if (key.equals(e.getKey())) |
| return e.getValue(); |
| } |
| } |
| return null; |
| } |
| |
| |
| // Modification Operations |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @implSpec |
| * This implementation always throws an |
| * <tt>UnsupportedOperationException</tt>. |
| * |
| * @throws UnsupportedOperationException {@inheritDoc} |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| * @throws IllegalArgumentException {@inheritDoc} |
| */ |
| public V put(K key, V value) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @implSpec |
| * This implementation iterates over <tt>entrySet()</tt> searching for an |
| * entry with the specified key. If such an entry is found, its value is |
| * obtained with its <tt>getValue</tt> operation, the entry is removed |
| * from the collection (and the backing map) with the iterator's |
| * <tt>remove</tt> operation, and the saved value is returned. If the |
| * iteration terminates without finding such an entry, <tt>null</tt> is |
| * returned. Note that this implementation requires linear time in the |
| * size of the map; many implementations will override this method. |
| * |
| * <p>Note that this implementation throws an |
| * <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt> |
| * iterator does not support the <tt>remove</tt> method and this map |
| * contains a mapping for the specified key. |
| * |
| * @throws UnsupportedOperationException {@inheritDoc} |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| */ |
| public V remove(Object key) { |
| Iterator<Entry<K,V>> i = entrySet().iterator(); |
| Entry<K,V> correctEntry = null; |
| if (key==null) { |
| while (correctEntry==null && i.hasNext()) { |
| Entry<K,V> e = i.next(); |
| if (e.getKey()==null) |
| correctEntry = e; |
| } |
| } else { |
| while (correctEntry==null && i.hasNext()) { |
| Entry<K,V> e = i.next(); |
| if (key.equals(e.getKey())) |
| correctEntry = e; |
| } |
| } |
| |
| V oldValue = null; |
| if (correctEntry !=null) { |
| oldValue = correctEntry.getValue(); |
| i.remove(); |
| } |
| return oldValue; |
| } |
| |
| |
| // Bulk Operations |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @implSpec |
| * This implementation iterates over the specified map's |
| * <tt>entrySet()</tt> collection, and calls this map's <tt>put</tt> |
| * operation once for each entry returned by the iteration. |
| * |
| * <p>Note that this implementation throws an |
| * <tt>UnsupportedOperationException</tt> if this map does not support |
| * the <tt>put</tt> operation and the specified map is nonempty. |
| * |
| * @throws UnsupportedOperationException {@inheritDoc} |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| * @throws IllegalArgumentException {@inheritDoc} |
| */ |
| public void putAll(Map<? extends K, ? extends V> m) { |
| for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) |
| put(e.getKey(), e.getValue()); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @implSpec |
| * This implementation calls <tt>entrySet().clear()</tt>. |
| * |
| * <p>Note that this implementation throws an |
| * <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt> |
| * does not support the <tt>clear</tt> operation. |
| * |
| * @throws UnsupportedOperationException {@inheritDoc} |
| */ |
| public void clear() { |
| entrySet().clear(); |
| } |
| |
| |
| // Views |
| |
| /** |
| * Each of these fields are initialized to contain an instance of the |
| * appropriate view the first time this view is requested. The views are |
| * stateless, so there's no reason to create more than one of each. |
| * |
| * <p>Since there is no synchronization performed while accessing these fields, |
| * it is expected that java.util.Map view classes using these fields have |
| * no non-final fields (or any fields at all except for outer-this). Adhering |
| * to this rule would make the races on these fields benign. |
| * |
| * <p>It is also imperative that implementations read the field only once, |
| * as in: |
| * |
| * <pre> {@code |
| * public Set<K> keySet() { |
| * Set<K> ks = keySet; // single racy read |
| * if (ks == null) { |
| * ks = new KeySet(); |
| * keySet = ks; |
| * } |
| * return ks; |
| * } |
| *}</pre> |
| */ |
| transient Set<K> keySet; |
| transient Collection<V> values; |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @implSpec |
| * This implementation returns a set that subclasses {@link AbstractSet}. |
| * The subclass's iterator method returns a "wrapper object" over this |
| * map's <tt>entrySet()</tt> iterator. The <tt>size</tt> method |
| * delegates to this map's <tt>size</tt> method and the |
| * <tt>contains</tt> method delegates to this map's |
| * <tt>containsKey</tt> method. |
| * |
| * <p>The set is created the first time this method is called, |
| * and returned in response to all subsequent calls. No synchronization |
| * is performed, so there is a slight chance that multiple calls to this |
| * method will not all return the same set. |
| */ |
| public Set<K> keySet() { |
| Set<K> ks = keySet; |
| if (ks == null) { |
| ks = new AbstractSet<K>() { |
| public Iterator<K> iterator() { |
| return new Iterator<K>() { |
| private Iterator<Entry<K,V>> i = entrySet().iterator(); |
| |
| public boolean hasNext() { |
| return i.hasNext(); |
| } |
| |
| public K next() { |
| return i.next().getKey(); |
| } |
| |
| public void remove() { |
| i.remove(); |
| } |
| }; |
| } |
| |
| public int size() { |
| return AbstractMap.this.size(); |
| } |
| |
| public boolean isEmpty() { |
| return AbstractMap.this.isEmpty(); |
| } |
| |
| public void clear() { |
| AbstractMap.this.clear(); |
| } |
| |
| public boolean contains(Object k) { |
| return AbstractMap.this.containsKey(k); |
| } |
| }; |
| keySet = ks; |
| } |
| return ks; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * @implSpec |
| * This implementation returns a collection that subclasses {@link |
| * AbstractCollection}. The subclass's iterator method returns a |
| * "wrapper object" over this map's <tt>entrySet()</tt> iterator. |
| * The <tt>size</tt> method delegates to this map's <tt>size</tt> |
| * method and the <tt>contains</tt> method delegates to this map's |
| * <tt>containsValue</tt> method. |
| * |
| * <p>The collection is created the first time this method is called, and |
| * returned in response to all subsequent calls. No synchronization is |
| * performed, so there is a slight chance that multiple calls to this |
| * method will not all return the same collection. |
| */ |
| public Collection<V> values() { |
| Collection<V> vals = values; |
| if (vals == null) { |
| vals = new AbstractCollection<V>() { |
| public Iterator<V> iterator() { |
| return new Iterator<V>() { |
| private Iterator<Entry<K,V>> i = entrySet().iterator(); |
| |
| public boolean hasNext() { |
| return i.hasNext(); |
| } |
| |
| public V next() { |
| return i.next().getValue(); |
| } |
| |
| public void remove() { |
| i.remove(); |
| } |
| }; |
| } |
| |
| public int size() { |
| return AbstractMap.this.size(); |
| } |
| |
| public boolean isEmpty() { |
| return AbstractMap.this.isEmpty(); |
| } |
| |
| public void clear() { |
| AbstractMap.this.clear(); |
| } |
| |
| public boolean contains(Object v) { |
| return AbstractMap.this.containsValue(v); |
| } |
| }; |
| values = vals; |
| } |
| return vals; |
| } |
| |
| public abstract Set<Entry<K,V>> entrySet(); |
| |
| |
| // Comparison and hashing |
| |
| /** |
| * Compares the specified object with this map for equality. Returns |
| * <tt>true</tt> if the given object is also a map and the two maps |
| * represent the same mappings. More formally, two maps <tt>m1</tt> and |
| * <tt>m2</tt> represent the same mappings if |
| * <tt>m1.entrySet().equals(m2.entrySet())</tt>. This ensures that the |
| * <tt>equals</tt> method works properly across different implementations |
| * of the <tt>Map</tt> interface. |
| * |
| * @implSpec |
| * This implementation first checks if the specified object is this map; |
| * if so it returns <tt>true</tt>. Then, it checks if the specified |
| * object is a map whose size is identical to the size of this map; if |
| * not, it returns <tt>false</tt>. If so, it iterates over this map's |
| * <tt>entrySet</tt> collection, and checks that the specified map |
| * contains each mapping that this map contains. If the specified map |
| * fails to contain such a mapping, <tt>false</tt> is returned. If the |
| * iteration completes, <tt>true</tt> is returned. |
| * |
| * @param o object to be compared for equality with this map |
| * @return <tt>true</tt> if the specified object is equal to this map |
| */ |
| public boolean equals(Object o) { |
| if (o == this) |
| return true; |
| |
| if (!(o instanceof Map)) |
| return false; |
| Map<?,?> m = (Map<?,?>) o; |
| if (m.size() != size()) |
| return false; |
| |
| try { |
| Iterator<Entry<K,V>> i = entrySet().iterator(); |
| while (i.hasNext()) { |
| Entry<K,V> e = i.next(); |
| K key = e.getKey(); |
| V value = e.getValue(); |
| if (value == null) { |
| if (!(m.get(key)==null && m.containsKey(key))) |
| return false; |
| } else { |
| if (!value.equals(m.get(key))) |
| return false; |
| } |
| } |
| } catch (ClassCastException unused) { |
| return false; |
| } catch (NullPointerException unused) { |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /** |
| * Returns the hash code value for this map. The hash code of a map is |
| * defined to be the sum of the hash codes of each entry in the map's |
| * <tt>entrySet()</tt> view. This ensures that <tt>m1.equals(m2)</tt> |
| * implies that <tt>m1.hashCode()==m2.hashCode()</tt> for any two maps |
| * <tt>m1</tt> and <tt>m2</tt>, as required by the general contract of |
| * {@link Object#hashCode}. |
| * |
| * @implSpec |
| * This implementation iterates over <tt>entrySet()</tt>, calling |
| * {@link Map.Entry#hashCode hashCode()} on each element (entry) in the |
| * set, and adding up the results. |
| * |
| * @return the hash code value for this map |
| * @see Map.Entry#hashCode() |
| * @see Object#equals(Object) |
| * @see Set#equals(Object) |
| */ |
| public int hashCode() { |
| int h = 0; |
| Iterator<Entry<K,V>> i = entrySet().iterator(); |
| while (i.hasNext()) |
| h += i.next().hashCode(); |
| return h; |
| } |
| |
| /** |
| * Returns a string representation of this map. The string representation |
| * consists of a list of key-value mappings in the order returned by the |
| * map's <tt>entrySet</tt> view's iterator, enclosed in braces |
| * (<tt>"{}"</tt>). Adjacent mappings are separated by the characters |
| * <tt>", "</tt> (comma and space). Each key-value mapping is rendered as |
| * the key followed by an equals sign (<tt>"="</tt>) followed by the |
| * associated value. Keys and values are converted to strings as by |
| * {@link String#valueOf(Object)}. |
| * |
| * @return a string representation of this map |
| */ |
| public String toString() { |
| Iterator<Entry<K,V>> i = entrySet().iterator(); |
| if (! i.hasNext()) |
| return "{}"; |
| |
| StringBuilder sb = new StringBuilder(); |
| sb.append('{'); |
| for (;;) { |
| Entry<K,V> e = i.next(); |
| K key = e.getKey(); |
| V value = e.getValue(); |
| sb.append(key == this ? "(this Map)" : key); |
| sb.append('='); |
| sb.append(value == this ? "(this Map)" : value); |
| if (! i.hasNext()) |
| return sb.append('}').toString(); |
| sb.append(',').append(' '); |
| } |
| } |
| |
| /** |
| * Returns a shallow copy of this <tt>AbstractMap</tt> instance: the keys |
| * and values themselves are not cloned. |
| * |
| * @return a shallow copy of this map |
| */ |
| protected Object clone() throws CloneNotSupportedException { |
| AbstractMap<?,?> result = (AbstractMap<?,?>)super.clone(); |
| result.keySet = null; |
| result.values = null; |
| return result; |
| } |
| |
| /** |
| * Utility method for SimpleEntry and SimpleImmutableEntry. |
| * Test for equality, checking for nulls. |
| * |
| * NB: Do not replace with Object.equals until JDK-8015417 is resolved. |
| */ |
| private static boolean eq(Object o1, Object o2) { |
| return o1 == null ? o2 == null : o1.equals(o2); |
| } |
| |
| // Implementation Note: SimpleEntry and SimpleImmutableEntry |
| // are distinct unrelated classes, even though they share |
| // some code. Since you can't add or subtract final-ness |
| // of a field in a subclass, they can't share representations, |
| // and the amount of duplicated code is too small to warrant |
| // exposing a common abstract class. |
| |
| |
| /** |
| * An Entry maintaining a key and a value. The value may be |
| * changed using the <tt>setValue</tt> method. This class |
| * facilitates the process of building custom map |
| * implementations. For example, it may be convenient to return |
| * arrays of <tt>SimpleEntry</tt> instances in method |
| * <tt>Map.entrySet().toArray</tt>. |
| * |
| * @since 1.6 |
| */ |
| public static class SimpleEntry<K,V> |
| implements Entry<K,V>, java.io.Serializable |
| { |
| private static final long serialVersionUID = -8499721149061103585L; |
| |
| private final K key; |
| private V value; |
| |
| /** |
| * Creates an entry representing a mapping from the specified |
| * key to the specified value. |
| * |
| * @param key the key represented by this entry |
| * @param value the value represented by this entry |
| */ |
| public SimpleEntry(K key, V value) { |
| this.key = key; |
| this.value = value; |
| } |
| |
| /** |
| * Creates an entry representing the same mapping as the |
| * specified entry. |
| * |
| * @param entry the entry to copy |
| */ |
| public SimpleEntry(Entry<? extends K, ? extends V> entry) { |
| this.key = entry.getKey(); |
| this.value = entry.getValue(); |
| } |
| |
| /** |
| * Returns the key corresponding to this entry. |
| * |
| * @return the key corresponding to this entry |
| */ |
| public K getKey() { |
| return key; |
| } |
| |
| /** |
| * Returns the value corresponding to this entry. |
| * |
| * @return the value corresponding to this entry |
| */ |
| public V getValue() { |
| return value; |
| } |
| |
| /** |
| * Replaces the value corresponding to this entry with the specified |
| * value. |
| * |
| * @param value new value to be stored in this entry |
| * @return the old value corresponding to the entry |
| */ |
| public V setValue(V value) { |
| V oldValue = this.value; |
| this.value = value; |
| return oldValue; |
| } |
| |
| /** |
| * Compares the specified object with this entry for equality. |
| * Returns {@code true} if the given object is also a map entry and |
| * the two entries represent the same mapping. More formally, two |
| * entries {@code e1} and {@code e2} represent the same mapping |
| * if<pre> |
| * (e1.getKey()==null ? |
| * e2.getKey()==null : |
| * e1.getKey().equals(e2.getKey())) |
| * && |
| * (e1.getValue()==null ? |
| * e2.getValue()==null : |
| * e1.getValue().equals(e2.getValue()))</pre> |
| * This ensures that the {@code equals} method works properly across |
| * different implementations of the {@code Map.Entry} interface. |
| * |
| * @param o object to be compared for equality with this map entry |
| * @return {@code true} if the specified object is equal to this map |
| * entry |
| * @see #hashCode |
| */ |
| public boolean equals(Object o) { |
| if (!(o instanceof Map.Entry)) |
| return false; |
| Map.Entry<?,?> e = (Map.Entry<?,?>)o; |
| return eq(key, e.getKey()) && eq(value, e.getValue()); |
| } |
| |
| /** |
| * Returns the hash code value for this map entry. The hash code |
| * of a map entry {@code e} is defined to be: <pre> |
| * (e.getKey()==null ? 0 : e.getKey().hashCode()) ^ |
| * (e.getValue()==null ? 0 : e.getValue().hashCode())</pre> |
| * This ensures that {@code e1.equals(e2)} implies that |
| * {@code e1.hashCode()==e2.hashCode()} for any two Entries |
| * {@code e1} and {@code e2}, as required by the general |
| * contract of {@link Object#hashCode}. |
| * |
| * @return the hash code value for this map entry |
| * @see #equals |
| */ |
| public int hashCode() { |
| return (key == null ? 0 : key.hashCode()) ^ |
| (value == null ? 0 : value.hashCode()); |
| } |
| |
| /** |
| * Returns a String representation of this map entry. This |
| * implementation returns the string representation of this |
| * entry's key followed by the equals character ("<tt>=</tt>") |
| * followed by the string representation of this entry's value. |
| * |
| * @return a String representation of this map entry |
| */ |
| public String toString() { |
| return key + "=" + value; |
| } |
| |
| } |
| |
| /** |
| * An Entry maintaining an immutable key and value. This class |
| * does not support method <tt>setValue</tt>. This class may be |
| * convenient in methods that return thread-safe snapshots of |
| * key-value mappings. |
| * |
| * @since 1.6 |
| */ |
| public static class SimpleImmutableEntry<K,V> |
| implements Entry<K,V>, java.io.Serializable |
| { |
| private static final long serialVersionUID = 7138329143949025153L; |
| |
| private final K key; |
| private final V value; |
| |
| /** |
| * Creates an entry representing a mapping from the specified |
| * key to the specified value. |
| * |
| * @param key the key represented by this entry |
| * @param value the value represented by this entry |
| */ |
| public SimpleImmutableEntry(K key, V value) { |
| this.key = key; |
| this.value = value; |
| } |
| |
| /** |
| * Creates an entry representing the same mapping as the |
| * specified entry. |
| * |
| * @param entry the entry to copy |
| */ |
| public SimpleImmutableEntry(Entry<? extends K, ? extends V> entry) { |
| this.key = entry.getKey(); |
| this.value = entry.getValue(); |
| } |
| |
| /** |
| * Returns the key corresponding to this entry. |
| * |
| * @return the key corresponding to this entry |
| */ |
| public K getKey() { |
| return key; |
| } |
| |
| /** |
| * Returns the value corresponding to this entry. |
| * |
| * @return the value corresponding to this entry |
| */ |
| public V getValue() { |
| return value; |
| } |
| |
| /** |
| * Replaces the value corresponding to this entry with the specified |
| * value (optional operation). This implementation simply throws |
| * <tt>UnsupportedOperationException</tt>, as this class implements |
| * an <i>immutable</i> map entry. |
| * |
| * @param value new value to be stored in this entry |
| * @return (Does not return) |
| * @throws UnsupportedOperationException always |
| */ |
| public V setValue(V value) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * Compares the specified object with this entry for equality. |
| * Returns {@code true} if the given object is also a map entry and |
| * the two entries represent the same mapping. More formally, two |
| * entries {@code e1} and {@code e2} represent the same mapping |
| * if<pre> |
| * (e1.getKey()==null ? |
| * e2.getKey()==null : |
| * e1.getKey().equals(e2.getKey())) |
| * && |
| * (e1.getValue()==null ? |
| * e2.getValue()==null : |
| * e1.getValue().equals(e2.getValue()))</pre> |
| * This ensures that the {@code equals} method works properly across |
| * different implementations of the {@code Map.Entry} interface. |
| * |
| * @param o object to be compared for equality with this map entry |
| * @return {@code true} if the specified object is equal to this map |
| * entry |
| * @see #hashCode |
| */ |
| public boolean equals(Object o) { |
| if (!(o instanceof Map.Entry)) |
| return false; |
| Map.Entry<?,?> e = (Map.Entry<?,?>)o; |
| return eq(key, e.getKey()) && eq(value, e.getValue()); |
| } |
| |
| /** |
| * Returns the hash code value for this map entry. The hash code |
| * of a map entry {@code e} is defined to be: <pre> |
| * (e.getKey()==null ? 0 : e.getKey().hashCode()) ^ |
| * (e.getValue()==null ? 0 : e.getValue().hashCode())</pre> |
| * This ensures that {@code e1.equals(e2)} implies that |
| * {@code e1.hashCode()==e2.hashCode()} for any two Entries |
| * {@code e1} and {@code e2}, as required by the general |
| * contract of {@link Object#hashCode}. |
| * |
| * @return the hash code value for this map entry |
| * @see #equals |
| */ |
| public int hashCode() { |
| return (key == null ? 0 : key.hashCode()) ^ |
| (value == null ? 0 : value.hashCode()); |
| } |
| |
| /** |
| * Returns a String representation of this map entry. This |
| * implementation returns the string representation of this |
| * entry's key followed by the equals character ("<tt>=</tt>") |
| * followed by the string representation of this entry's value. |
| * |
| * @return a String representation of this map entry |
| */ |
| public String toString() { |
| return key + "=" + value; |
| } |
| |
| } |
| |
| } |
