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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 23:37:01 PDT 2000 --><TITLE>Java 2 Platform SE v1.3: Class Timer</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/Timer.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/StringTokenizer.html"><B>PREV CLASS</B></A> <A HREF="../../java/util/TimerTask.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="Timer.html" TARGET="_top"><B>NO FRAMES</B></A></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2"> SUMMARY: INNER | FIELD | <A HREF="#constructor_summary">CONSTR</A> | <A HREF="#method_summary">METHOD</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">DETAIL: FIELD | <A HREF="#constructor_detail">CONSTR</A> | <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>Class Timer</H2><PRE><A HREF="../../java/lang/Object.html">java.lang.Object</A> | +--<B>java.util.Timer</B></PRE><HR><DL><DT>public class <B>Timer</B><DT>extends <A HREF="../../java/lang/Object.html">Object</A></DL><P>A facility for threads to schedule tasks for future execution in a background thread. Tasks may be scheduled for one-time execution, or for repeated execution at regular intervals. <p>Corresponding to each <tt>Timer</tt> object is a single background thread that is used to execute all of the timer's tasks, sequentially. Timer tasks should complete quickly. If a timer task takes excessive time to complete, it "hogs" the timer's task execution thread. This can, in turn, delay the execution of subsequent tasks, which may "bunch up" and execute in rapid succession when (and if) the offending task finally completes. <p>After the last live reference to a <tt>Timer</tt> object goes away <i>and</i> all outstanding tasks have completed execution, the timer's task execution thread terminates gracefully (and becomes subject to garbage collection). However, this can take arbitrarily long to occur. By default, the task execution thread does not run as a <i>daemon thread</i>, so it is capable of keeping an application from terminating. If a caller wants to terminate a timer's task execution thread rapidly, the caller should invoke the the timer's <tt>cancel</tt> method. <p>If the timer's task execution thread terminates unexpectedly, for example, because its <tt>stop</tt> method is invoked, any further attempt to schedule a task on the timer will result in an <tt>IllegalStateException</tt>, as if the timer's <tt>cancel</tt> method had been invoked. <p>This class is thread-safe: multiple threads can share a single <tt>Timer</tt> object without the need for external synchronization. <p>This class does <i>not</i> offer real-time guarantees: it schedules tasks using the <tt>Object.wait(long)</tt> method. <p>Implementation note: This class scales to large numbers of concurrently scheduled tasks (thousands should present no problem). Internally, it uses a binary heap to represent its task queue, so the cost to schedule a task is O(log n), where n is the number of concurrently scheduled tasks.<P><DL><DT><B>Since: </B><DD>1.3</DD><DT><B>See Also: </B><DD><A HREF="../../java/util/TimerTask.html"><CODE>TimerTask</CODE></A>, <A HREF="../../java/lang/Object.html#wait(long)"><CODE>Object.wait(long)</CODE></A></DL><HR><P><!-- ======== INNER CLASS SUMMARY ======== --><!-- =========== FIELD SUMMARY =========== --><!-- ======== CONSTRUCTOR SUMMARY ======== --><A NAME="constructor_summary"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Constructor Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><B><A HREF="../../java/util/Timer.html#Timer()">Timer</A></B>()</CODE><BR> Creates a new timer.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><B><A HREF="../../java/util/Timer.html#Timer(boolean)">Timer</A></B>(boolean isDaemon)</CODE><BR> Creates a new timer whose associated thread may be specified to run as a daemon.</TD></TR></TABLE> <!-- ========== 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/Timer.html#cancel()">cancel</A></B>()</CODE><BR> Terminates this timer, discarding any currently scheduled tasks.</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/Timer.html#schedule(java.util.TimerTask, java.util.Date)">schedule</A></B>(<A HREF="../../java/util/TimerTask.html">TimerTask</A> task, <A HREF="../../java/util/Date.html">Date</A> time)</CODE><BR> Schedules the specified task for execution at the specified time.</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/Timer.html#schedule(java.util.TimerTask, java.util.Date, long)">schedule</A></B>(<A HREF="../../java/util/TimerTask.html">TimerTask</A> task, <A HREF="../../java/util/Date.html">Date</A> firstTime, long period)</CODE><BR> Schedules the specified task for repeated <i>fixed-delay execution</i>, beginning at the specified time.</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/Timer.html#schedule(java.util.TimerTask, long)">schedule</A></B>(<A HREF="../../java/util/TimerTask.html">TimerTask</A> task, long delay)</CODE><BR> Schedules the specified task for execution after the specified delay.</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/Timer.html#schedule(java.util.TimerTask, long, long)">schedule</A></B>(<A HREF="../../java/util/TimerTask.html">TimerTask</A> task, long delay, long period)</CODE><BR> Schedules the specified task for repeated <i>fixed-delay execution</i>, beginning after the specified delay.</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/Timer.html#scheduleAtFixedRate(java.util.TimerTask, java.util.Date, long)">scheduleAtFixedRate</A></B>(<A HREF="../../java/util/TimerTask.html">TimerTask</A> task, <A HREF="../../java/util/Date.html">Date</A> firstTime, long period)</CODE><BR> Schedules the specified task for repeated <i>fixed-rate execution</i>, beginning at the specified time.</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/Timer.html#scheduleAtFixedRate(java.util.TimerTask, long, long)">scheduleAtFixedRate</A></B>(<A HREF="../../java/util/TimerTask.html">TimerTask</A> task, long delay, long period)</CODE><BR> Schedules the specified task for repeated <i>fixed-rate execution</i>, beginning after the specified delay.</TD></TR></TABLE> <A NAME="methods_inherited_from_class_java.lang.Object"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#EEEEFF" CLASS="TableSubHeadingColor"><TD><B>Methods inherited from class java.lang.<A HREF="../../java/lang/Object.html">Object</A></B></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><A HREF="../../java/lang/Object.html#clone()">clone</A>, <A HREF="../../java/lang/Object.html#equals(java.lang.Object)">equals</A>, <A HREF="../../java/lang/Object.html#finalize()">finalize</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#toString()">toString</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></TR></TABLE> <P><!-- ============ FIELD DETAIL =========== --><!-- ========= CONSTRUCTOR DETAIL ======== --><A NAME="constructor_detail"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=1><FONT SIZE="+2"><B>Constructor Detail</B></FONT></TD></TR></TABLE><A NAME="Timer()"><!-- --></A><H3>Timer</H3><PRE>public <B>Timer</B>()</PRE><DL><DD>Creates a new timer. The associated thread does <i>not</i> run as a daemon.<DD><DL><DT><B>See Also: </B><DD><A HREF="../../java/lang/Thread.html"><CODE>Thread</CODE></A>, <A HREF="../../java/util/Timer.html#cancel()"><CODE>cancel()</CODE></A></DL></DD>⌨️ 快捷键说明
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