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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><!--NewPage--><HTML><HEAD><!-- Generated by javadoc (build 1.5.0_07) on Thu Jun 21 14:48:20 PDT 2007 --><TITLE>Cache (Smack 3.0.4 Documentation)</TITLE><META NAME="keywords" CONTENT="org.jivesoftware.smack.util.Cache class"><LINK REL ="stylesheet" TYPE="text/css" HREF="../../../../stylesheet.css" TITLE="Style"><SCRIPT type="text/javascript">function windowTitle(){ parent.document.title="Cache (Smack 3.0.4 Documentation)";}</SCRIPT><NOSCRIPT></NOSCRIPT></HEAD><BODY BGCOLOR="white" onload="windowTitle();"><!-- ========= START OF TOP NAVBAR ======= --><A NAME="navbar_top"><!-- --></A><A HREF="#skip-navbar_top" title="Skip navigation links"></A><TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0" SUMMARY=""><TR><TD COLSPAN=2 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"><A NAME="navbar_top_firstrow"><!-- --></A><TABLE BORDER="0" CELLPADDING="0" CELLSPACING="3" SUMMARY=""> <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="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-all.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>Smack</b></EM></TD></TR><TR><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../../../org/jivesoftware/smack/util/Base64.OutputStream.html" title="class in org.jivesoftware.smack.util"><B>PREV CLASS</B></A> <A HREF="../../../../org/jivesoftware/smack/util/DNSUtil.html" title="class in org.jivesoftware.smack.util"><B>NEXT CLASS</B></A></FONT></TD><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../../../index.html?org/jivesoftware/smack/util/Cache.html" target="_top"><B>FRAMES</B></A> <A HREF="Cache.html" target="_top"><B>NO FRAMES</B></A> <SCRIPT type="text/javascript"> <!-- if(window==top) { document.writeln('<A HREF="../../../../allclasses-noframe.html"><B>All Classes</B></A>'); } //--></SCRIPT><NOSCRIPT> <A HREF="../../../../allclasses-noframe.html"><B>All Classes</B></A></NOSCRIPT></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2"> SUMMARY: NESTED | <A HREF="#field_summary">FIELD</A> | <A HREF="#constructor_summary">CONSTR</A> | <A HREF="#method_summary">METHOD</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">DETAIL: <A HREF="#field_detail">FIELD</A> | <A HREF="#constructor_detail">CONSTR</A> | <A HREF="#method_detail">METHOD</A></FONT></TD></TR></TABLE><A NAME="skip-navbar_top"></A><!-- ========= END OF TOP NAVBAR ========= --><HR><!-- ======== START OF CLASS DATA ======== --><H2><FONT SIZE="-1">org.jivesoftware.smack.util</FONT><BR>Class Cache<K,V></H2><PRE><A HREF="http://java.sun.com/j2se/1.3/docs/api/java/lang/Object.html" title="class or interface in java.lang">java.lang.Object</A> <IMG SRC="../../../../resources/inherit.gif" ALT="extended by "><B>org.jivesoftware.smack.util.Cache<K,V></B></PRE><DL><DT><B>All Implemented Interfaces:</B> <DD><A HREF="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.html" title="class or interface in java.util">Map</A><K,V></DD></DL><HR><DL><DT><PRE>public class <B>Cache<K,V></B><DT>extends <A HREF="http://java.sun.com/j2se/1.3/docs/api/java/lang/Object.html" title="class or interface in java.lang">Object</A><DT>implements <A HREF="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.html" title="class or interface in java.util">Map</A><K,V></DL></PRE><P>A specialized Map that is size-limited (using an LRU algorithm) and has an optional expiration time for cache items. The Map is thread-safe.<p> The algorithm for cache is as follows: a HashMap is maintained for fast object lookup. Two linked lists are maintained: one keeps objects in the order they are accessed from cache, the other keeps objects in the order they were originally added to cache. When objects are added to cache, they are first wrapped by a CacheObject which maintains the following pieces of information:<ul> <li> A pointer to the node in the linked list that maintains accessed order for the object. Keeping a reference to the node lets us avoid linear scans of the linked list. <li> A pointer to the node in the linked list that maintains the age of the object in cache. Keeping a reference to the node lets us avoid linear scans of the linked list.</ul> <p/> To get an object from cache, a hash lookup is performed to get a reference to the CacheObject that wraps the real object we are looking for. The object is subsequently moved to the front of the accessed linked list and any necessary cache cleanups are performed. Cache deletion and expiration is performed as needed.<P><P><DL><DT><B>Author:</B></DT> <DD>Matt Tucker</DD></DL><HR><P><!-- ======== NESTED CLASS SUMMARY ======== --><A NAME="nested_class_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TH ALIGN="left" COLSPAN="2"><FONT SIZE="+2"><B>Nested Class Summary</B></FONT></TH></TR></TABLE> <A NAME="nested_classes_inherited_from_class_java.util.Map"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#EEEEFF" CLASS="TableSubHeadingColor"><TH ALIGN="left"><B>Nested classes/interfaces inherited from interface java.util.<A HREF="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.html" title="class or interface in java.util">Map</A></B></TH></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><A HREF="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.Entry.html" title="class or interface in java.util">Map.Entry</A><<A HREF="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.Entry.html" title="class or interface in java.util">K</A>,<A HREF="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.Entry.html" title="class or interface in java.util">V</A>></CODE></TD></TR></TABLE> <!-- =========== FIELD SUMMARY =========== --><A NAME="field_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TH ALIGN="left" COLSPAN="2"><FONT SIZE="+2"><B>Field Summary</B></FONT></TH></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected org.jivesoftware.smack.util.Cache.LinkedList</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#ageList">ageList</A></B></CODE><BR> Linked list to maintain time that cache objects were initially added to the cache, most recently added to oldest added.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected long</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#cacheHits">cacheHits</A></B></CODE><BR> Maintain the number of cache hits and misses.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected long</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#cacheMisses">cacheMisses</A></B></CODE><BR> Maintain the number of cache hits and misses.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected org.jivesoftware.smack.util.Cache.LinkedList</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#lastAccessedList">lastAccessedList</A></B></CODE><BR> Linked list to maintain order that cache objects are accessed in, most used to least used.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected <A HREF="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.html" title="class or interface in java.util">Map</A><<A HREF="../../../../org/jivesoftware/smack/util/Cache.html" title="type parameter in Cache">K</A>,org.jivesoftware.smack.util.Cache.CacheObject<<A HREF="../../../../org/jivesoftware/smack/util/Cache.html" title="type parameter in Cache">V</A>>></CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#map">map</A></B></CODE><BR> The map the keys and values are stored in.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected int</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#maxCacheSize">maxCacheSize</A></B></CODE><BR> Maximum number of items the cache will hold.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected long</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#maxLifetime">maxLifetime</A></B></CODE><BR> Maximum length of time objects can exist in cache before expiring.</TD></TR></TABLE> <!-- ======== CONSTRUCTOR SUMMARY ======== --><A NAME="constructor_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TH ALIGN="left" COLSPAN="2"><FONT SIZE="+2"><B>Constructor Summary</B></FONT></TH></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#Cache(int, long)">Cache</A></B>(int maxSize, long maxLifetime)</CODE><BR> Create a new cache and specify the maximum size of for the cache in bytes, and the maximum lifetime of objects.</TD></TR></TABLE> <!-- ========== METHOD SUMMARY =========== --><A NAME="method_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TH ALIGN="left" COLSPAN="2"><FONT SIZE="+2"><B>Method Summary</B></FONT></TH></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="../../../../org/jivesoftware/smack/util/Cache.html#clear()">clear</A></B>()</CODE><BR> </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="../../../../org/jivesoftware/smack/util/Cache.html#containsKey(java.lang.Object)">containsKey</A></B>(<A HREF="http://java.sun.com/j2se/1.3/docs/api/java/lang/Object.html" title="class or interface in java.lang">Object</A> key)</CODE><BR> </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="../../../../org/jivesoftware/smack/util/Cache.html#containsValue(java.lang.Object)">containsValue</A></B>(<A HREF="http://java.sun.com/j2se/1.3/docs/api/java/lang/Object.html" title="class or interface in java.lang">Object</A> value)</CODE><BR> </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected void</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#cullCache()">cullCache</A></B>()</CODE><BR> Removes the least recently used elements if the cache size is greater than or equal to the maximum allowed size until the cache is at least 10% empty.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected void</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#deleteExpiredEntries()">deleteExpiredEntries</A></B>()</CODE><BR> Clears all entries out of cache where the entries are older than the maximum defined age.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="http://java.sun.com/j2se/1.3/docs/api/java/util/Set.html" title="class or interface in java.util">Set</A><<A HREF="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.Entry.html" title="class or interface in java.util">Map.Entry</A><<A HREF="../../../../org/jivesoftware/smack/util/Cache.html" title="type parameter in Cache">K</A>,<A HREF="../../../../org/jivesoftware/smack/util/Cache.html" title="type parameter in Cache">V</A>>></CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#entrySet()">entrySet</A></B>()</CODE><BR> </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../../../org/jivesoftware/smack/util/Cache.html" title="type parameter in Cache">V</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#get(java.lang.Object)">get</A></B>(<A HREF="http://java.sun.com/j2se/1.3/docs/api/java/lang/Object.html" title="class or interface in java.lang">Object</A> key)</CODE><BR> </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> long</CODE></FONT></TD><TD><CODE><B><A HREF="../../../../org/jivesoftware/smack/util/Cache.html#getCacheHits()">getCacheHits</A></B>()</CODE><BR> </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> long</CODE></FONT></TD>⌨️ 快捷键说明
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