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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN""http://www.w3.org/TR/REC-html40/frameset.dtd"><!--NewPage--><HTML><HEAD><!-- Generated by javadoc on Thu Apr 27 23:36:44 PDT 2000 --><TITLE>Java 2 Platform SE v1.3: Interface Map</TITLE><LINK REL ="stylesheet" TYPE="text/css" HREF="../../stylesheet.css" TITLE="Style"></HEAD><BODY BGCOLOR="white"><!-- ========== START OF NAVBAR ========== --><A NAME="navbar_top"><!-- --></A><TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0"><TR><TD COLSPAN=2 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"><A NAME="navbar_top_firstrow"><!-- --></A><TABLE BORDER="0" CELLPADDING="0" CELLSPACING="3"> <TR ALIGN="center" VALIGN="top"> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../overview-summary.html"><FONT CLASS="NavBarFont1"><B>Overview</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-summary.html"><FONT CLASS="NavBarFont1"><B>Package</B></FONT></A> </TD> <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> <FONT CLASS="NavBarFont1Rev"><B>Class</B></FONT> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="class-use/Map.html"><FONT CLASS="NavBarFont1"><B>Use</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>Tree</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../deprecated-list.html"><FONT CLASS="NavBarFont1"><B>Deprecated</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../index-files/index-1.html"><FONT CLASS="NavBarFont1"><B>Index</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../help-doc.html"><FONT CLASS="NavBarFont1"><B>Help</B></FONT></A> </TD> </TR></TABLE></TD><TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM><b>Java<sup><font size=-2>TM</font></sup> 2 Platform<br>Std. Ed. v1.3</b></EM></TD></TR><TR><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../java/util/ListIterator.html"><B>PREV CLASS</B></A> <A HREF="../../java/util/Map.Entry.html"><B>NEXT CLASS</B></A></FONT></TD><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../index.html" TARGET="_top"><B>FRAMES</B></A> <A HREF="Map.html" TARGET="_top"><B>NO FRAMES</B></A></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2"> SUMMARY: <A HREF="#inner_class_summary">INNER</A> | FIELD | CONSTR | <A HREF="#method_summary">METHOD</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">DETAIL: FIELD | CONSTR | <A HREF="#method_detail">METHOD</A></FONT></TD></TR></TABLE><!-- =========== END OF NAVBAR =========== --><HR><!-- ======== START OF CLASS DATA ======== --><H2><FONT SIZE="-1">java.util</FONT><BR>Interface Map</H2><DL><DT><B>All Known Subinterfaces:</B> <DD><A HREF="../../java/util/SortedMap.html">SortedMap</A></DD></DL><DL><DT><B>All Known Implementing Classes:</B> <DD><A HREF="../../java/util/AbstractMap.html">AbstractMap</A>, <A HREF="../../java/util/HashMap.html">HashMap</A>, <A HREF="../../java/util/Hashtable.html">Hashtable</A>, <A HREF="../../java/awt/RenderingHints.html">RenderingHints</A>, <A HREF="../../java/util/WeakHashMap.html">WeakHashMap</A>, <A HREF="../../java/util/jar/Attributes.html">Attributes</A></DD></DL><HR><DL><DT>public interface <B>Map</B></DL><P>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><DL><DT><B>Since: </B><DD>1.2</DD><DT><B>See Also: </B><DD><A HREF="../../java/util/HashMap.html"><CODE>HashMap</CODE></A>, <A HREF="../../java/util/TreeMap.html"><CODE>TreeMap</CODE></A>, <A HREF="../../java/util/Hashtable.html"><CODE>Hashtable</CODE></A>, <A HREF="../../java/util/SortedMap.html"><CODE>SortedMap</CODE></A>, <A HREF="../../java/util/Collection.html"><CODE>Collection</CODE></A>, <A HREF="../../java/util/Set.html"><CODE>Set</CODE></A></DL><HR><P><!-- ======== INNER CLASS SUMMARY ======== --><A NAME="inner_class_summary"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Inner Class Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static interface</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.Entry.html">Map.Entry</A></B></CODE><BR> A map entry (key-value pair).</TD></TR></TABLE> <!-- =========== FIELD SUMMARY =========== --><!-- ======== CONSTRUCTOR SUMMARY ======== --><!-- ========== METHOD SUMMARY =========== --><A NAME="method_summary"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Method Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> void</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.html#clear()">clear</A></B>()</CODE><BR> Removes all mappings from this map (optional operation).</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> boolean</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.html#containsKey(java.lang.Object)">containsKey</A></B>(<A HREF="../../java/lang/Object.html">Object</A> key)</CODE><BR> Returns <tt>true</tt> if this map contains a mapping for the specified key.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> boolean</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.html#containsValue(java.lang.Object)">containsValue</A></B>(<A HREF="../../java/lang/Object.html">Object</A> value)</CODE><BR> Returns <tt>true</tt> if this map maps one or more keys to the specified value.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/util/Set.html">Set</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.html#entrySet()">entrySet</A></B>()</CODE><BR> Returns a set view of the mappings contained in this map.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> boolean</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.html#equals(java.lang.Object)">equals</A></B>(<A HREF="../../java/lang/Object.html">Object</A> o)</CODE><BR> Compares the specified object with this map for equality.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><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/Map.html#get(java.lang.Object)">get</A></B>(<A HREF="../../java/lang/Object.html">Object</A> key)</CODE><BR> Returns the value to which this map maps the specified key.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> int</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.html#hashCode()">hashCode</A></B>()</CODE><BR> Returns the hash code value for this map.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> boolean</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.html#isEmpty()">isEmpty</A></B>()</CODE><BR> Returns <tt>true</tt> if this map contains no key-value mappings.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/util/Set.html">Set</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.html#keySet()">keySet</A></B>()</CODE><BR> Returns a set view of the keys contained in this map.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><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/Map.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> Associates the specified value with the specified key in this map (optional operation).</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> void</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.html#putAll(java.util.Map)">putAll</A></B>(<A HREF="../../java/util/Map.html">Map</A> t)</CODE><BR> Copies all of the mappings from the specified map to this map (optional operation).</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><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/Map.html#remove(java.lang.Object)">remove</A></B>(<A HREF="../../java/lang/Object.html">Object</A> key)</CODE><BR> Removes the mapping for this key from this map if present (optional operation).</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> int</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.html#size()">size</A></B>()</CODE><BR> Returns the number of key-value mappings in this map.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/util/Collection.html">Collection</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/util/Map.html#values()">values</A></B>()</CODE><BR> Returns a collection view of the values contained in this map.</TD></TR></TABLE> <P><!-- ============ FIELD DETAIL =========== --><!-- ========= CONSTRUCTOR DETAIL ======== --><!-- ============ METHOD DETAIL ========== --><A NAME="method_detail"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=1><FONT SIZE="+2"><B>Method Detail</B></FONT></TD></TR></TABLE><A NAME="size()"><!-- --></A><H3>size</H3><PRE>public int <B>size</B>()</PRE>⌨️ 快捷键说明
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