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134 lines
4.5 KiB
Java
134 lines
4.5 KiB
Java
/* Dictionary.java -- an abstract (and essentially worthless)
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class which is Hashtable's superclass
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Copyright (C) 1998, 2001 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.util;
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/**
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* A Dictionary maps keys to values; <i>how</i> it does that is
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* implementation-specific.
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*
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* This is an abstract class which has really gone by the wayside.
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* People at Javasoft are probably embarrassed by it. At this point,
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* it might as well be an interface rather than a class, but it remains
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* this poor, laughable skeleton for the sake of backwards compatibility.
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* At any rate, this was what came before the <pre>Map</pre> interface
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* in the Collections framework.
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*
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* @author Jon Zeppieri
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* @author Eric Blake <ebb9@email.byu.edu>
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* @see Map
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* @see Hashtable
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* @since 1.0
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* @status updated to 1.4
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*/
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public abstract class Dictionary extends Object
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{
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/**
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* Sole constructor (often called implicitly).
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*/
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public Dictionary()
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{
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}
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/**
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* Returns an Enumeration of the values in this Dictionary.
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*
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* @return an Enumeration of the values
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* @see #keys()
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*/
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public abstract Enumeration elements();
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/**
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* Returns the value associated with the supplied key, or null
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* if no such value exists. Since Dictionaries are not allowed null keys
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* or elements, a null result always means the key is not present.
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*
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* @param key the key to use to fetch the value
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* @return the mapped value
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* @throws NullPointerException if key is null
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* @see #put(Object, Object)
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*/
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public abstract Object get(Object key);
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/**
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* Returns true when there are no elements in this Dictionary.
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*
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* @return <code>size() == 0</code>
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*/
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public abstract boolean isEmpty();
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/**
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* Returns an Enumeration of the keys in this Dictionary
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*
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* @return an Enumeration of the keys
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* @see #elements()
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*/
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public abstract Enumeration keys();
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/**
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* Inserts a new value into this Dictionary, located by the
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* supplied key. Dictionary does not support null keys or values, so
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* a null return can safely be interpreted as adding a new key.
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*
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* @param key the key which locates the value
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* @param value the value to put into the Dictionary
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* @return the previous value of the key, or null if there was none
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* @throws NullPointerException if key or value is null
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* @see #get(Object)
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*/
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public abstract Object put(Object key, Object value);
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/**
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* Removes from the Dictionary the value located by the given key. A null
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* return safely means that the key was not mapped in the Dictionary.
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*
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* @param key the key used to locate the value to be removed
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* @return the value associated with the removed key
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* @throws NullPointerException if key is null
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*/
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public abstract Object remove(Object key);
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/**
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* Returns the number of values currently in this Dictionary.
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*
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* @return the number of keys in the Dictionary
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*/
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public abstract int size();
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}
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