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MID Profile: Class Hashtable
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java.util</FONT>
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Class Hashtable</H2>
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<A HREF="../../java/lang/Object.html">java.lang.Object</A>
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+--<B>java.util.Hashtable</B>
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<DT>public class <B>Hashtable</B><DT>extends <A HREF="../../java/lang/Object.html">Object</A></DL>
<P>
This class implements a hashtable, which maps keys to values. Any non-<code>null</code> object can be used as a key or as a value. <p> To successfully store and retrieve objects from a hashtable, the objects used as keys must implement the <code>hashCode</code> method and the <code>equals</code> method. <p> An instance of <code>Hashtable</code> has two parameters that affect its efficiency: its <i>capacity</i> and its <i>load factor</i>. The load factor should be between 0.0 and 1.0. When the number of entries in the hashtable exceeds the product of the load factor and the current capacity, the capacity is increased by calling the <code>rehash</code> method. Larger load factors use memory more efficiently, at the expense of larger expected time per lookup. <p> If many entries are to be made into a <code>Hashtable</code>, creating it with a sufficiently large capacity may allow the entries to be inserted more efficiently than letting it perform automatic rehashing as needed to grow the table. <p> This example creates a hashtable of numbers. It uses the names of the numbers as keys: <p><blockquote><pre> Hashtable numbers = new Hashtable(); numbers.put("one", new Integer(1)); numbers.put("two", new Integer(2)); numbers.put("three", new Integer(3)); </pre></blockquote> <p> To retrieve a number, use the following code: <p><blockquote><pre> Integer n = (Integer)numbers.get("two"); if (n != null) { System.out.println("two = " + n); } </pre></blockquote> <p> Note: To conserve space, the CLDC implementation is based on JDK 1.1.8, not JDK 1.3.
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<DT><B>Since: </B><DD>JDK1.0, CLDC 1.0</DD>
<DT><B>See Also: </B><DD><A HREF="../../java/lang/Object.html#equals(java.lang.Object)"><CODE>Object.equals(java.lang.Object)</CODE></A>,
<A HREF="../../java/lang/Object.html#hashCode()"><CODE>Object.hashCode()</CODE></A>,
<A HREF="../../java/util/Hashtable.html#rehash()"><CODE>rehash()</CODE></A></DL>
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<TD><CODE><B><A HREF="../../java/util/Hashtable.html#Hashtable()">Hashtable</A></B>()</CODE>
<BR>
Constructs a new, empty hashtable with a default capacity and load factor.</TD>
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<TD><CODE><B><A HREF="../../java/util/Hashtable.html#Hashtable(int)">Hashtable</A></B>(int initialCapacity)</CODE>
<BR>
Constructs a new, empty hashtable with the specified initial capacity.</TD>
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<CODE> void</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#clear()">clear</A></B>()</CODE>
<BR>
Clears this hashtable so that it contains no keys.</TD>
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<CODE> boolean</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#contains(java.lang.Object)">contains</A></B>(<A HREF="../../java/lang/Object.html">Object</A> value)</CODE>
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Tests if some key maps into the specified value in this hashtable.</TD>
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<CODE> boolean</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#containsKey(java.lang.Object)">containsKey</A></B>(<A HREF="../../java/lang/Object.html">Object</A> key)</CODE>
<BR>
Tests if the specified object is a key in this hashtable.</TD>
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<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
<CODE> <A HREF="../../java/util/Enumeration.html">Enumeration</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#elements()">elements</A></B>()</CODE>
<BR>
Returns an enumeration of the values in this hashtable.</TD>
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<CODE> <A HREF="../../java/lang/Object.html">Object</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#get(java.lang.Object)">get</A></B>(<A HREF="../../java/lang/Object.html">Object</A> key)</CODE>
<BR>
Returns the value to which the specified key is mapped in this hashtable.</TD>
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<CODE> boolean</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#isEmpty()">isEmpty</A></B>()</CODE>
<BR>
Tests if this hashtable maps no keys to values.</TD>
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<CODE> <A HREF="../../java/util/Enumeration.html">Enumeration</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#keys()">keys</A></B>()</CODE>
<BR>
Returns an enumeration of the keys in this hashtable.</TD>
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<CODE> <A HREF="../../java/lang/Object.html">Object</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#put(java.lang.Object, java.lang.Object)">put</A></B>(<A HREF="../../java/lang/Object.html">Object</A> key, <A HREF="../../java/lang/Object.html">Object</A> value)</CODE>
<BR>
Maps the specified <code>key</code> to the specified <code>value</code> in this hashtable.</TD>
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<CODE>protected void</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#rehash()">rehash</A></B>()</CODE>
<BR>
Rehashes the contents of the hashtable into a hashtable with a larger capacity.</TD>
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<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
<CODE> <A HREF="../../java/lang/Object.html">Object</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#remove(java.lang.Object)">remove</A></B>(<A HREF="../../java/lang/Object.html">Object</A> key)</CODE>
<BR>
Removes the key (and its corresponding value) from this hashtable.</TD>
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<CODE> int</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#size()">size</A></B>()</CODE>
<BR>
Returns the number of keys in this hashtable.</TD>
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<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
<CODE> <A HREF="../../java/lang/String.html">String</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../java/util/Hashtable.html#toString()">toString</A></B>()</CODE>
<BR>
Returns a rather long string representation of this hashtable.</TD>
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<TD><B>Methods inherited from class java.lang.<A HREF="../../java/lang/Object.html">Object</A></B></TD>
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<TR BGCOLOR="white" CLASS="TableRowColor">
<TD><CODE><A HREF="../../java/lang/Object.html#equals(java.lang.Object)">equals</A>, <A HREF="../../java/lang/Object.html#getClass()">getClass</A>, <A HREF="../../java/lang/Object.html#hashCode()">hashCode</A>, <A HREF="../../java/lang/Object.html#notify()">notify</A>, <A HREF="../../java/lang/Object.html#notifyAll()">notifyAll</A>, <A HREF="../../java/lang/Object.html#wait()">wait</A>, <A HREF="../../java/lang/Object.html#wait(long)">wait</A>, <A HREF="../../java/lang/Object.html#wait(long, int)">wait</A></CODE></TD>
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