/*
* @(#)Map.java 1.39 03/01/23
*
* Copyright 2003 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package instrumented.java.util;
/**
* An object that maps keys to values. A map cannot contain duplicate keys;
* each key can map to at most one value.
*
* <p>This interface takes the place of the <tt>Dictionary</tt> class, which
* was a totally abstract class rather than an interface.
*
* <p>The <tt>Map</tt> interface provides three <i>collection views</i>, which
* allow a map's contents to be viewed as a set of keys, collection of values,
* or set of key-value mappings. The <i>order</i> of a map is defined as
* the order in which the iterators on the map's collection views return their
* elements. Some map implementations, like the <tt>TreeMap</tt> class, make
* specific guarantees as to their order; others, like the <tt>HashMap</tt>
* class, do not.
*
* <p>Note: great care must be exercised if mutable objects are used as map
* keys. The behavior of a map is not specified if the value of an object is
* changed in a manner that affects equals comparisons while the object is a
* key in the map. A special case of this prohibition is that it is not
* permissible for a map to contain itself as a key. While it is permissible
* for a map to contain itself as a value, extreme caution is advised: the
* equals and hashCode methods are no longer well defined on a such a map.
*
* <p>All general-purpose map implementation classes should provide two
* "standard" constructors: a void (no arguments) constructor which creates an
* empty map, and a constructor with a single argument of type <tt>Map</tt>,
* which creates a new map with the same key-value mappings as its argument.
* In effect, the latter constructor allows the user to copy any map,
* producing an equivalent map of the desired class. There is no way to
* enforce this recommendation (as interfaces cannot contain constructors) but
* all of the general-purpose map implementations in the SDK comply.
*
* <p>The "destructive" methods contained in this interface, that is, the
* methods that modify the map on which they operate, are specified to throw
* <tt>UnsupportedOperationException</tt> if this map does not support the
* operation. If this is the case, these methods may, but are not required
* to, throw an <tt>UnsupportedOperationException</tt> if the invocation would
* have no effect on the map. For example, invoking the {@link #putAll(Map)}
* method on an unmodifiable map may, but is not required to, throw the
* exception if the map whose mappings are to be "superimposed" is empty.
*
* <p>Some map implementations have restrictions on the keys and values they
* may contain. For example, some implementations prohibit null keys and
* values, and some have restrictions on the types of their keys. Attempting
* to insert an ineligible key or value throws an unchecked exception,
* typically <tt>NullPointerException</tt> or <tt>ClassCastException</tt>.
* Attempting to query the presence of an ineligible key or value may throw an
* exception, or it may simply return false; some implementations will exhibit
* the former behavior and some will exhibit the latter. More generally,
* attempting an operation on an ineligible key or value whose completion
* would not result in the insertion of an ineligible element into the map may
* throw an exception or it may succeed, at the option of the implementation.
* Such exceptions are marked as "optional" in the specification for this
* interface.
*
* <p>This interface is a member of the
* <a href="{@docRoot}/../guide/collections/index.html">
* Java Collections Framework</a>.
*
* @author Josh Bloch
* @version 1.39, 01/23/03
* @see HashMap
* @see TreeMap
* @see Hashtable
* @see SortedMap
* @see Collection
* @see Set
* @since 1.2
*/
public interface Map {
// Query Operations
/**
* Returns the number of key-value mappings in this map. If the
* map contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
* <tt>Integer.MAX_VALUE</tt>.
*
* @return the number of key-value mappings in this map.
*/
int size();
/**
* Returns <tt>true</tt> if this map contains no key-value mappings.
*
* @return <tt>true</tt> if this map contains no key-value mappings.
*/
boolean isEmpty();
/**
* Returns <tt>true</tt> if this map contains a mapping for the specified
* key. More formally, returns <tt>true</tt> if and only if
* this map contains at a mapping for a key <tt>k</tt> such that
* <tt>(key==null ? k==null : key.equals(k))</tt>. (There can be
* at most one such mapping.)
*
* @param key key whose presence in this map is to be tested.
* @return <tt>true</tt> if this map contains a mapping for the specified
* key.
*
* @throws ClassCastException if the key is of an inappropriate type for
* this map (optional).
* @throws NullPointerException if the key is <tt>null</tt> and this map
* does not not permit <tt>null</tt> keys (optional).
*/
boolean containsKey(Object key);
/**
* Returns <tt>true</tt> if this map maps one or more keys to the
* specified value. More formally, returns <tt>true</tt> if and only if
* this map contains at least one mapping to a value <tt>v</tt> such that
* <tt>(value==null ? v==null : value.equals(v))</tt>. This operation
* will probably require time linear in the map size for most
* implementations of the <tt>Map</tt> interface.
*
* @param value value whose presence in this map is to be tested.
* @return <tt>true</tt> if this map maps one or more keys to the
* specified value.
* @throws ClassCastException if the value is of an inappropriate type for
* this map (optional).
* @throws NullPointerException if the value is <tt>null</tt> and this map
* does not not permit <tt>null</tt> values (optional).
*/
boolean containsValue(Object value);
/**
* Returns the value to which this map maps the specified key. Returns
* <tt>null</tt> if the map contains no mapping for this key. A return
* value of <tt>null</tt> does not <i>necessarily</i> indicate that the
* map contains no mapping for the key; it's also possible that the map
* explicitly maps the key to <tt>null</tt>. The <tt>containsKey</tt>
* operation may be used to distinguish these two cases.
*
* <p>More formally, if this map contains a mapping from a key
* <tt>k</tt> to a value <tt>v</tt> such that <tt>(key==null ? k==null :
* key.equals(k))</tt>, then this method returns <tt>v</tt>; otherwise
* it returns <tt>null</tt>. (There can be at most one such mapping.)
*
* @param key key whose associated value is to be returned.
* @return the value to which this map maps the specified key, or
* <tt>null</tt> if the map contains no mapping for this key.
*
* @throws ClassCastException if the key is of an inappropriate type for
* this map (optional).
* @throws NullPointerException key is <tt>null</tt> and this map does not
* not permit <tt>null</tt> keys (optional).
*
* @see #containsKey(Object)
*/
Object get(Object key);
// Modification Operations
/**
* Associates the specified value with the specified key in this map
* (optional operation). If the map previously contained a mapping for
* this key, the old value is replaced by the specified value. (A map
* <tt>m</tt> is said to contain a mapping for a key <tt>k</tt> if and only
* if {@link #containsKey(Object) m.containsKey(k)} would return
* <tt>true</tt>.))
*
* @param key key with which the specified value is to be associated.
* @param value value to be associated with the specified key.
* @return previous value associated with specified key, or <tt>null</tt>
* if there was no mapping for key. A <tt>null</tt> return can
* also indicate that the map previously associated <tt>null</tt>
* with the specified key, if the implementation supports
* <tt>null</tt> values.
*
* @throws UnsupportedOperationException if the <tt>put</tt> operation is
* not supported by this map.
* @throws ClassCastException if the class of the specified key or value
* prevents it from being stored in this map.
* @throws IllegalArgumentException if some aspect of this key or value
* prevents it from being stored in this map.
* @throws NullPointerException this map does not permit <tt>null</tt>
* keys or values, and the specified key or value is
* <tt>null</tt>.
*/
Object put(Object key, Object value);
/**
* Removes the mapping for this key from this map if it is present
* (optional operation). More formally, if this map contains a mapping
* from key <tt>k</tt> to value <tt>v</tt> such that
* <code>(key==null ? k==null : key.equals(k))</code>, that mapping
* is removed. (The map can contain at most one such mapping.)
*
* <p>Returns the value to which the map previously associated the key, or
* <tt>null</tt> if the map contained no mapping for this key. (A
* <tt>null</tt> return can also indicate that the map previously
* associated <tt>null</tt> with the specified key if the implementation
* supports <tt>null</tt> values.) The map will not contain a mapping for
* the specified key once the call returns.
*
* @param key key whose mapping is to be removed from the map.
* @return previous value associated with specified key, or <tt>null</tt>
* if there was no mapping for key.
*
* @throws ClassCastException if the key is of an inappropriate type for
* this map (optional).
* @throws NullPointerException if the key is <tt>null</tt> and this map
* does not not permit <tt>null</tt> keys (optional).
* @throws UnsupportedOperationException if the <tt>remove</tt> method is
* not supported by this map.
*/
Object remove(Object key);
// Bulk Operations
/**
* Copies all of the mappings from the specified map to this map
* (optional operation). The effect of this call is equivalent to that
* of calling {@link #put(Object,Object) put(k, v)} on this map once
* for each mapping from key <tt>k</tt> to value <tt>v</tt> in the
* specified map. The behavior of this operation is unspecified if the
* specified map is modified while the operation is in progress.
*
* @param t Mappings to be stored in this map.
*
* @throws UnsupportedOperationException if the <tt>putAll</tt> method is
* not supported by this map.
*
* @throws ClassCastException if the class of a key or value in the
* specified map prevents it from being stored in this map.
*
* @throws IllegalArgumentException some aspect of a key or value in the
* specified map prevents it from being stored in this map.
* @throws NullPointerException the specified map is <tt>null</tt>, or if
* this map does not permit <tt>null</tt> keys or values, and the
* specified map contains <tt>null</tt> keys or values.
*/
void putAll(Map t);
/**
* Removes all mappings from this map (optional operation).
*
* @throws UnsupportedOperationException clear is not supported by this
* map.
*/
void clear();
// Views
/**
* Returns a set view of the keys contained in this map. The set is
* backed by the map, so changes to the map are reflected in the set, and
* vice-versa. If the map is modified while an iteration over the set is
* in progress, the results of the iteration are undefined. The set
* supports element removal, which removes the corresponding mapping from
* the map, via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
* <tt>removeAll</tt> <tt>retainAll</tt>, and <tt>clear</tt> operations.
* It does not support the add or <tt>addAll</tt> operations.
*
* @return a set view of the keys contained in this map.
*/
Set keySet();
/**
* Returns a collection view of the values contained in this map. The
* collection is backed by the map, so changes to the map are reflected in
* the collection, and vice-versa. If the map is modified while an
* iteration over the collection is in progress, the results of the
* iteration are undefined. The collection supports element removal,
* which removes the corresponding mapping from the map, via the
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt> and <tt>clear</tt> operations.
* It does not support the add or <tt>addAll</tt> operations.
*
* @return a collection view of the values contained in this map.
*/
Collection values();
/**
* Returns a set view of the mappings contained in this map. Each element
* in the returned set is a {@link Map.Entry}. The set is backed by the
* map, so changes to the map are reflected in the set, and vice-versa.
* If the map is modified while an iteration over the set is in progress,
* the results of the iteration are undefined. The set supports element
* removal, which removes the corresponding mapping from the map, via the
* <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, <tt>removeAll</tt>,
* <tt>retainAll</tt> and <tt>clear</tt> operations. It does not support
* the <tt>add</tt> or <tt>addAll</tt> operations.
*
* @return a set view of the mappings contained in this map.
*/
Set entrySet();
/**
* A map entry (key-value pair). The <tt>Map.entrySet</tt> method returns
* a collection-view of the map, whose elements are of this class. The
* <i>only</i> way to obtain a reference to a map entry is from the
* iterator of this collection-view. These <tt>Map.Entry</tt> objects are
* valid <i>only</i> for the duration of the iteration; more formally,
* the behavior of a map entry is undefined if the backing map has been
* modified after the entry was returned by the iterator, except through
* the iterator's own <tt>remove</tt> operation, or through the
* <tt>setValue</tt> operation on a map entry returned by the iterator.
*
* @see Map#entrySet()
* @since 1.2
*/
interface Entry {
/**
* Returns the key corresponding to this entry.
*
* @return the key corresponding to this entry.
*/
Object getKey();
/**
* Returns the value corresponding to this entry. If the mapping
* has been removed from the backing map (by the iterator's
* <tt>remove</tt> operation), the results of this call are undefined.
*
* @return the value corresponding to this entry.
*/
Object getValue();
/**
* Replaces the value corresponding to this entry with the specified
* value (optional operation). (Writes through to the map.) The
* behavior of this call is undefined if the mapping has already been
* removed from the map (by the iterator's <tt>remove</tt> operation).
*
* @param value new value to be stored in this entry.
* @return old value corresponding to the entry.
*
* @throws UnsupportedOperationException if the <tt>put</tt> operation
* is not supported by the backing map.
* @throws ClassCastException if the class of the specified value
* prevents it from being stored in the backing map.
* @throws IllegalArgumentException if some aspect of this value
* prevents it from being stored in the backing map.
* @throws NullPointerException the backing map does not permit
* <tt>null</tt> values, and the specified value is
* <tt>null</tt>.
*/
Object setValue(Object value);
/**
* Compares the specified object with this entry for equality.
* Returns <tt>true</tt> if the given object is also a map entry and
* the two entries represent the same mapping. More formally, two
* entries <tt>e1</tt> and <tt>e2</tt> 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 <tt>equals</tt> method works properly across
* different implementations of the <tt>Map.Entry</tt> interface.
*
* @param o object to be compared for equality with this map entry.
* @return <tt>true</tt> if the specified object is equal to this map
* entry.
*/
boolean equals(Object o);
/**
* Returns the hash code value for this map entry. The hash code
* of a map entry <tt>e</tt> is defined to be: <pre>
* (e.getKey()==null ? 0 : e.getKey().hashCode()) ^
* (e.getValue()==null ? 0 : e.getValue().hashCode())
* </pre>
* This ensures that <tt>e1.equals(e2)</tt> implies that
* <tt>e1.hashCode()==e2.hashCode()</tt> for any two Entries
* <tt>e1</tt> and <tt>e2</tt>, as required by the general
* contract of <tt>Object.hashCode</tt>.
*
* @return the hash code value for this map entry.
* @see Object#hashCode()
* @see Object#equals(Object)
* @see #equals(Object)
*/
int hashCode();
}
// 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>t1</tt> and
* <tt>t2</tt> represent the same mappings if
* <tt>t1.entrySet().equals(t2.entrySet())</tt>. This ensures that the
* <tt>equals</tt> method works properly across different implementations
* of the <tt>Map</tt> interface.
*
* @param o object to be compared for equality with this map.
* @return <tt>true</tt> if the specified object is equal to this map.
*/
boolean equals(Object o);
/**
* Returns the hash code value for this map. The hash code of a map
* is defined to be the sum of the hashCodes of each entry in the map's
* entrySet view. This ensures that <tt>t1.equals(t2)</tt> implies
* that <tt>t1.hashCode()==t2.hashCode()</tt> for any two maps
* <tt>t1</tt> and <tt>t2</tt>, as required by the general
* contract of Object.hashCode.
*
* @return the hash code value for this map.
* @see Map.Entry#hashCode()
* @see Object#hashCode()
* @see Object#equals(Object)
* @see #equals(Object)
*/
int hashCode();
}