- /*
- * Copyright 2003-2004 The Apache Software Foundation
- *
- * Licensed 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.collections.map;
-
- import java.io.Serializable;
- import java.util.AbstractSet;
- import java.util.Collection;
- import java.util.Collections;
- import java.util.Iterator;
- import java.util.Map;
- import java.util.NoSuchElementException;
- import java.util.Set;
-
- import org.apache.commons.collections.BoundedMap;
- import org.apache.commons.collections.KeyValue;
- import org.apache.commons.collections.MapIterator;
- import org.apache.commons.collections.OrderedMap;
- import org.apache.commons.collections.OrderedMapIterator;
- import org.apache.commons.collections.ResettableIterator;
- import org.apache.commons.collections.iterators.SingletonIterator;
- import org.apache.commons.collections.keyvalue.TiedMapEntry;
-
- /**
- * A <code>Map</code> implementation that holds a single item and is fixed size.
- * <p>
- * The single key/value pair is specified at creation.
- * The map is fixed size so any action that would change the size is disallowed.
- * However, the <code>put</code> or <code>setValue</code> methods can <i>change</i>
- * the value associated with the key.
- * <p>
- * If trying to remove or clear the map, an UnsupportedOperationException is thrown.
- * If trying to put a new mapping into the map, an IllegalArgumentException is thrown.
- * The put method will only suceed if the key specified is the same as the
- * singleton key.
- * <p>
- * The key and value can be obtained by:
- * <ul>
- * <li>normal Map methods and views
- * <li>the <code>MapIterator</code>, see {@link #mapIterator()}
- * <li>the <code>KeyValue</code> interface (just cast - no object creation)
- * </ul>
- *
- * @since Commons Collections 3.1
- * @version $Revision: 1.1 $ $Date: 2004/04/09 14:46:35 $
- *
- * @author Stephen Colebourne
- */
- public class SingletonMap
- implements OrderedMap, BoundedMap, KeyValue, Serializable, Cloneable {
-
- /** Serialization version */
- private static final long serialVersionUID = -8931271118676803261L;
-
- /** Singleton key */
- private final Object key;
- /** Singleton value */
- private Object value;
-
- /**
- * Constructor that creates a map of <code>null</code> to <code>null</code>.
- */
- public SingletonMap() {
- super();
- this.key = null;
- }
-
- /**
- * Constructor specifying the key and value.
- *
- * @param key the key to use
- * @param value the value to use
- */
- public SingletonMap(Object key, Object value) {
- super();
- this.key = key;
- this.value = value;
- }
-
- /**
- * Constructor specifying the key and value as a <code>KeyValue</code>.
- *
- * @param keyValue the key value pair to use
- */
- public SingletonMap(KeyValue keyValue) {
- super();
- this.key = keyValue.getKey();
- this.value = keyValue.getValue();
- }
-
- /**
- * Constructor specifying the key and value as a <code>MapEntry</code>.
- *
- * @param keyValue the key value pair to use
- */
- public SingletonMap(Map.Entry entry) {
- super();
- this.key = entry.getKey();
- this.value = entry.getValue();
- }
-
- /**
- * Constructor copying elements from another map.
- *
- * @param map the map to copy, must be size 1
- * @throws NullPointerException if the map is null
- * @throws IllegalArgumentException if the size is not 1
- */
- public SingletonMap(Map map) {
- super();
- if (map.size() != 1) {
- throw new IllegalArgumentException("The map size must be 1");
- }
- Map.Entry entry = (Map.Entry) map.entrySet().iterator().next();
- this.key = entry.getKey();
- this.value = entry.getValue();
- }
-
- // KeyValue
- //-----------------------------------------------------------------------
- /**
- * Gets the key.
- *
- * @return the key
- */
- public Object getKey() {
- return key;
- }
-
- /**
- * Gets the value.
- *
- * @return the value
- */
- public Object getValue() {
- return value;
- }
-
- /**
- * Sets the value.
- *
- * @param value the new value to set
- * @return the old value
- */
- public Object setValue(Object value) {
- Object old = this.value;
- this.value = value;
- return old;
- }
-
- // BoundedMap
- //-----------------------------------------------------------------------
- /**
- * Is the map currently full, always true.
- *
- * @return true always
- */
- public boolean isFull() {
- return true;
- }
-
- /**
- * Gets the maximum size of the map, always 1.
- *
- * @return 1 always
- */
- public int maxSize() {
- return 1;
- }
-
- // Map
- //-----------------------------------------------------------------------
- /**
- * Gets the value mapped to the key specified.
- *
- * @param key the key
- * @return the mapped value, null if no match
- */
- public Object get(Object key) {
- if (isEqualKey(key)) {
- return value;
- }
- return null;
- }
-
- /**
- * Gets the size of the map, always 1.
- *
- * @return the size of 1
- */
- public int size() {
- return 1;
- }
-
- /**
- * Checks whether the map is currently empty, which it never is.
- *
- * @return false always
- */
- public boolean isEmpty() {
- return false;
- }
-
- //-----------------------------------------------------------------------
- /**
- * Checks whether the map contains the specified key.
- *
- * @param key the key to search for
- * @return true if the map contains the key
- */
- public boolean containsKey(Object key) {
- return (isEqualKey(key));
- }
-
- /**
- * Checks whether the map contains the specified value.
- *
- * @param value the value to search for
- * @return true if the map contains the key
- */
- public boolean containsValue(Object value) {
- return (isEqualValue(value));
- }
-
- //-----------------------------------------------------------------------
- /**
- * Puts a key-value mapping into this map where the key must match the existing key.
- * <p>
- * An IllegalArgumentException is thrown if the key does not match as the map
- * is fixed size.
- *
- * @param key the key to set, must be the key of the map
- * @param value the value to set
- * @return the value previously mapped to this key, null if none
- * @throws IllegalArgumentException if the key does not match
- */
- public Object put(Object key, Object value) {
- if (isEqualKey(key)) {
- return setValue(value);
- }
- throw new IllegalArgumentException("Cannot put new key/value pair - Map is fixed size singleton");
- }
-
- /**
- * Puts the values from the specified map into this map.
- * <p>
- * The map must be of size 0 or size 1.
- * If it is size 1, the key must match the key of this map otherwise an
- * IllegalArgumentException is thrown.
- *
- * @param map the map to add, must be size 0 or 1, and the key must match
- * @throws NullPointerException if the map is null
- * @throws IllegalArgumentException if the key does not match
- */
- public void putAll(Map map) {
- switch (map.size()) {
- case 0:
- return;
-
- case 1:
- Map.Entry entry = (Map.Entry) map.entrySet().iterator().next();
- put(entry.getKey(), entry.getValue());
- return;
-
- default:
- throw new IllegalArgumentException("The map size must be 0 or 1");
- }
- }
-
- /**
- * Unsupported operation.
- *
- * @param key the mapping to remove
- * @return the value mapped to the removed key, null if key not in map
- * @throws UnsupportedOperationException always
- */
- public Object remove(Object key) {
- throw new UnsupportedOperationException();
- }
-
- /**
- * Unsupported operation.
- */
- public void clear() {
- throw new UnsupportedOperationException();
- }
-
- //-----------------------------------------------------------------------
- /**
- * Gets the entrySet view of the map.
- * Changes made via <code>setValue</code> affect this map.
- * To simply iterate through the entries, use {@link #mapIterator()}.
- *
- * @return the entrySet view
- */
- public Set entrySet() {
- Map.Entry entry = new TiedMapEntry(this, getKey());
- return Collections.singleton(entry);
- }
-
- /**
- * Gets the unmodifiable keySet view of the map.
- * Changes made to the view affect this map.
- * To simply iterate through the keys, use {@link #mapIterator()}.
- *
- * @return the keySet view
- */
- public Set keySet() {
- return Collections.singleton(key);
- }
-
- /**
- * Gets the unmodifiable values view of the map.
- * Changes made to the view affect this map.
- * To simply iterate through the values, use {@link #mapIterator()}.
- *
- * @return the values view
- */
- public Collection values() {
- return new SingletonValues(this);
- }
-
- /**
- * Gets an iterator over the map.
- * Changes made to the iterator using <code>setValue</code> affect this map.
- * The <code>remove</code> method is unsupported.
- * <p>
- * A MapIterator returns the keys in the map. It also provides convenient
- * methods to get the key and value, and set the value.
- * It avoids the need to create an entrySet/keySet/values object.
- * It also avoids creating the Map Entry object.
- *
- * @return the map iterator
- */
- public MapIterator mapIterator() {
- return new SingletonMapIterator(this);
- }
-
- // OrderedMap
- //-----------------------------------------------------------------------
- /**
- * Obtains an <code>OrderedMapIterator</code> over the map.
- * <p>
- * A ordered map iterator is an efficient way of iterating over maps
- * in both directions.
- *
- * @return an ordered map iterator
- */
- public OrderedMapIterator orderedMapIterator() {
- return new SingletonMapIterator(this);
- }
-
- /**
- * Gets the first (and only) key in the map.
- *
- * @return the key
- */
- public Object firstKey() {
- return getKey();
- }
-
- /**
- * Gets the last (and only) key in the map.
- *
- * @return the key
- */
- public Object lastKey() {
- return getKey();
- }
-
- /**
- * Gets the next key after the key specified, always null.
- *
- * @param key the next key
- * @return null always
- */
- public Object nextKey(Object key) {
- return null;
- }
-
- /**
- * Gets the previous key before the key specified, always null.
- *
- * @param key the next key
- * @return null always
- */
- public Object previousKey(Object key) {
- return null;
- }
-
- //-----------------------------------------------------------------------
- /**
- * Compares the specified key to the stored key.
- *
- * @param key the key to compare
- * @return true if equal
- */
- protected boolean isEqualKey(Object key) {
- return (key == null ? getKey() == null : key.equals(getKey()));
- }
-
- /**
- * Compares the specified value to the stored value.
- *
- * @param value the value to compare
- * @return true if equal
- */
- protected boolean isEqualValue(Object value) {
- return (value == null ? getValue() == null : value.equals(getValue()));
- }
-
- //-----------------------------------------------------------------------
- /**
- * SingletonMapIterator.
- */
- static class SingletonMapIterator implements OrderedMapIterator, ResettableIterator {
- private final SingletonMap parent;
- private boolean hasNext = true;
- private boolean canGetSet = false;
-
- SingletonMapIterator(SingletonMap parent) {
- super();
- this.parent = parent;
- }
-
- public boolean hasNext() {
- return hasNext;
- }
-
- public Object next() {
- if (hasNext == false) {
- throw new NoSuchElementException(AbstractHashedMap.NO_NEXT_ENTRY);
- }
- hasNext = false;
- canGetSet = true;
- return parent.getKey();
- }
-
- public boolean hasPrevious() {
- return (hasNext == false);
- }
-
- public Object previous() {
- if (hasNext == true) {
- throw new NoSuchElementException(AbstractHashedMap.NO_PREVIOUS_ENTRY);
- }
- hasNext = true;
- return parent.getKey();
- }
-
- public void remove() {
- throw new UnsupportedOperationException();
- }
-
- public Object getKey() {
- if (canGetSet == false) {
- throw new IllegalStateException(AbstractHashedMap.GETKEY_INVALID);
- }
- return parent.getKey();
- }
-
- public Object getValue() {
- if (canGetSet == false) {
- throw new IllegalStateException(AbstractHashedMap.GETVALUE_INVALID);
- }
- return parent.getValue();
- }
-
- public Object setValue(Object value) {
- if (canGetSet == false) {
- throw new IllegalStateException(AbstractHashedMap.SETVALUE_INVALID);
- }
- return parent.setValue(value);
- }
-
- public void reset() {
- hasNext = true;
- }
-
- public String toString() {
- if (hasNext) {
- return "Iterator[]";
- } else {
- return "Iterator[" + getKey() + "=" + getValue() + "]";
- }
- }
- }
-
- /**
- * Values implementation for the SingletonMap.
- * This class is needed as values is a view that must update as the map updates.
- */
- static class SingletonValues extends AbstractSet implements Serializable {
- private static final long serialVersionUID = -3689524741863047872L;
- private final SingletonMap parent;
-
- SingletonValues(SingletonMap parent) {
- super();
- this.parent = parent;
- }
-
- public int size() {
- return 1;
- }
- public boolean isEmpty() {
- return false;
- }
- public boolean contains(Object object) {
- return parent.containsValue(object);
- }
- public void clear() {
- throw new UnsupportedOperationException();
- }
- public Iterator iterator() {
- return new SingletonIterator(parent.getValue(), false);
- }
- }
-
- //-----------------------------------------------------------------------
- /**
- * Clones the map without cloning the key or value.
- *
- * @return a shallow clone
- */
- public Object clone() {
- try {
- SingletonMap cloned = (SingletonMap) super.clone();
- return cloned;
- } catch (CloneNotSupportedException ex) {
- throw new InternalError();
- }
- }
-
- /**
- * Compares this map with another.
- *
- * @param obj the object to compare to
- * @return true if equal
- */
- public boolean equals(Object obj) {
- if (obj == this) {
- return true;
- }
- if (obj instanceof Map == false) {
- return false;
- }
- Map other = (Map) obj;
- if (other.size() != 1) {
- return false;
- }
- Map.Entry entry = (Map.Entry) other.entrySet().iterator().next();
- return isEqualKey(entry.getKey()) && isEqualValue(entry.getValue());
- }
-
- /**
- * Gets the standard Map hashCode.
- *
- * @return the hash code defined in the Map interface
- */
- public int hashCode() {
- return (getKey() == null ? 0 : getKey().hashCode()) ^
- (getValue() == null ? 0 : getValue().hashCode());
- }
-
- /**
- * Gets the map as a String.
- *
- * @return a string version of the map
- */
- public String toString() {
- return new StringBuffer(128)
- .append('{')
- .append((getKey() == this ? "(this Map)" : getKey()))
- .append('=')
- .append((getValue() == this ? "(this Map)" : getValue()))
- .append('}')
- .toString();
- }
-
- }