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*
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* accompanied this code).
*
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package java.util;
/**
* The {@code Dictionary} class is the abstract parent of any
* class, such as {@code Hashtable}, which maps keys to values.
* Every key and every value is an object. In any one {@code Dictionary}
* object, every key is associated with at most one value. Given a
* {@code Dictionary} and a key, the associated element can be looked up.
* Any non-{@code null} object can be used as a key and as a value.
* <p>
* As a rule, the {@code equals} method should be used by
* implementations of this class to decide if two keys are the same.
* <p>
* <strong>NOTE: This class is obsolete. New implementations should
* implement the Map interface, rather than extending this class.</strong>
*
* @author unascribed
* @see java.util.Map
* @see java.lang.Object#equals(java.lang.Object)
* @see java.lang.Object#hashCode()
* @see java.util.Hashtable
* @since 1.0
*/
public abstract
class Dictionary<K,V> {
/**
* Sole constructor. (For invocation by subclass constructors, typically
* implicit.)
*/
public Dictionary() {
}
/**
* Returns the number of entries (distinct keys) in this dictionary.
*
* @return the number of keys in this dictionary.
*/
public abstract int size();
/**
* Tests if this dictionary maps no keys to value. The general contract
* for the {@code isEmpty} method is that the result is true if and only
* if this dictionary contains no entries.
*
* @return {@code true} if this dictionary maps no keys to values;
* {@code false} otherwise.
*/
public abstract boolean isEmpty();
/**
* Returns an enumeration of the keys in this dictionary. The general
* contract for the keys method is that an {@code Enumeration} object
* is returned that will generate all the keys for which this dictionary
* contains entries.
*
* @return an enumeration of the keys in this dictionary.
* @see java.util.Dictionary#elements()
* @see java.util.Enumeration
*/
public abstract Enumeration<K> keys();
/**
* Returns an enumeration of the values in this dictionary. The general
* contract for the {@code elements} method is that an
* {@code Enumeration} is returned that will generate all the elements
* contained in entries in this dictionary.
*
* @return an enumeration of the values in this dictionary.
* @see java.util.Dictionary#keys()
* @see java.util.Enumeration
*/
public abstract Enumeration<V> elements();
/**
* Returns the value to which the key is mapped in this dictionary.
* The general contract for the {@code isEmpty} method is that if this
* dictionary contains an entry for the specified key, the associated
* value is returned; otherwise, {@code null} is returned.
*
* @return the value to which the key is mapped in this dictionary;
* @param key a key in this dictionary.
* {@code null} if the key is not mapped to any value in
* this dictionary.
* @exception NullPointerException if the {@code key} is {@code null}.
* @see java.util.Dictionary#put(java.lang.Object, java.lang.Object)
*/
public abstract V get(Object key);
/**
* Maps the specified {@code key} to the specified
* {@code value} in this dictionary. Neither the key nor the
* value can be {@code null}.
* <p>
* If this dictionary already contains an entry for the specified
* {@code key}, the value already in this dictionary for that
* {@code key} is returned, after modifying the entry to contain the
* new element. <p>If this dictionary does not already have an entry
* for the specified {@code key}, an entry is created for the
* specified {@code key} and {@code value}, and {@code null} is
* returned.
* <p>
* The {@code value} can be retrieved by calling the
* {@code get} method with a {@code key} that is equal to
* the original {@code key}.
*
* @param key the hashtable key.
* @param value the value.
* @return the previous value to which the {@code key} was mapped
* in this dictionary, or {@code null} if the key did not
* have a previous mapping.
* @exception NullPointerException if the {@code key} or
* {@code value} is {@code null}.
* @see java.lang.Object#equals(java.lang.Object)
* @see java.util.Dictionary#get(java.lang.Object)
*/
public abstract V put(K key, V value);
/**
* Removes the {@code key} (and its corresponding
* {@code value}) from this dictionary. This method does nothing
* if the {@code key} is not in this dictionary.
*
* @param key the key that needs to be removed.
* @return the value to which the {@code key} had been mapped in this
* dictionary, or {@code null} if the key did not have a
* mapping.
* @exception NullPointerException if {@code key} is {@code null}.
*/
public abstract V remove(Object key);
}