reference.html

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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_03) on Wed Nov 02 09:50:16 CST 2005 --><META http-equiv="Content-Type" content="text/html; charset=gb2312"><TITLE>Reference (Java 2 Platform SE 5.0)</TITLE><META NAME="keywords" CONTENT="java.lang.ref.Reference class"><LINK REL ="stylesheet" TYPE="text/css" HREF="../../../stylesheet.css" TITLE="Style"><SCRIPT type="text/javascript">function windowTitle(){    parent.document.title="Reference (Java 2 Platform SE 5.0)";}</SCRIPT><NOSCRIPT></NOSCRIPT></HEAD><BODY BGCOLOR="white" onload="windowTitle();"><!-- ========= START OF TOP NAVBAR ======= --><A NAME="navbar_top"><!-- --></A><A HREF="#skip-navbar_top" title="跳过导航链接"></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>概述</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="package-summary.html"><FONT CLASS="NavBarFont1"><B>软件包</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> &nbsp;<FONT CLASS="NavBarFont1Rev"><B>类</B></FONT>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="class-use/Reference.html"><FONT CLASS="NavBarFont1"><B>使用</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>树</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="../../../deprecated-list.html"><FONT CLASS="NavBarFont1"><B>已过时</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="../../../index-files/index-1.html"><FONT CLASS="NavBarFont1"><B>索引</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="../../../help-doc.html"><FONT CLASS="NavBarFont1"><B>帮助</B></FONT></A>&nbsp;</TD>  </TR></TABLE></TD><TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM><b>Java<sup><font size=-2>TM</font></sup>&nbsp;2&nbsp;Platform<br>Standard&nbsp;Ed. 5.0</b></EM></TD></TR><TR><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2">&nbsp;<A HREF="PhantomReference.html" title="java.lang.ref 中的类"><B>上一个类</B></A>&nbsp;&nbsp;<A HREF="ReferenceQueue.html" title="java.lang.ref 中的类"><B>下一个类</B></A></FONT></TD><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2">  <A HREF="../../../index.html@java_2Flang_2Fref_2FReference.html" target="_top"><B>框架</B></A>  &nbsp;&nbsp;<A HREF="Reference.html" target="_top"><B>无框架</B></A>  &nbsp;&nbsp;<SCRIPT type="text/javascript">  <!--  if(window==top) {    document.writeln('<A HREF="../../../allclasses-noframe.html"><B>所有类</B></A>');  }  //--></SCRIPT><NOSCRIPT>  <A HREF="../../../allclasses-noframe.html"><B>所有类</B></A></NOSCRIPT></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">  摘要:&nbsp;嵌套&nbsp;|&nbsp;字段&nbsp;|&nbsp;构造方法&nbsp;|&nbsp;<A HREF="#method_summary">方法</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">详细信息:&nbsp;字段&nbsp;|&nbsp;构造方法&nbsp;|&nbsp;<A HREF="#method_detail">方法</A></FONT></TD></TR></TABLE><A NAME="skip-navbar_top"></A><!-- ========= END OF TOP NAVBAR ========= --><HR><!-- ======== START OF CLASS DATA ======== --><H2><FONT SIZE="-1">java.lang.ref</FONT><BR>类 Reference&lt;T&gt;</H2><PRE><A HREF="../Object.html" title="java.lang 中的类">java.lang.Object</A>  <IMG SRC="../../../resources/inherit.gif" ALT="继承者 "><B>java.lang.ref.Reference&lt;T&gt;</B></PRE><DL><DT><B>直接已知子类:</B> <DD><A HREF="PhantomReference.html" title="java.lang.ref 中的类">PhantomReference</A>, <A HREF="SoftReference.html" title="java.lang.ref 中的类">SoftReference</A>, <A HREF="WeakReference.html" title="java.lang.ref 中的类">WeakReference</A></DD></DL><HR><DL><DT><PRE>public abstract class <B>Reference&lt;T&gt;</B><DT>extends <A HREF="../Object.html" title="java.lang 中的类">Object</A></DL></PRE><P>引用对象的抽象基类。此类定义了常用于所有引用对象的操作。因为引用对象是通过与垃圾回收器的密切合作来实现的,所以不能直接为此类创建子类。<P><P><DL><DT><B>从以下版本开始:</B></DT>  <DD>1.2</DD></DL><HR><P><!-- ========== 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>方法摘要</B></FONT></TH></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>&nbsp;void</CODE></FONT></TD><TD><CODE><B><A HREF="Reference.html#clear()">clear</A></B>()</CODE><BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;清除此引用对象。</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>&nbsp;boolean</CODE></FONT></TD><TD><CODE><B><A HREF="Reference.html#enqueue()">enqueue</A></B>()</CODE><BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;将此引用对象添加到引用对象已向其注册的队列(如果有)。</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>&nbsp;<A HREF="Reference.html" title="Reference 中的类型参数">T</A></CODE></FONT></TD><TD><CODE><B><A HREF="Reference.html#get()">get</A></B>()</CODE><BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;返回此引用对象的指示对象。</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>&nbsp;boolean</CODE></FONT></TD><TD><CODE><B><A HREF="Reference.html#isEnqueued()">isEnqueued</A></B>()</CODE><BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;由程序或垃圾回收器通知是否已将此引用对象加入队列。</TD></TR></TABLE>&nbsp;<A NAME="methods_inherited_from_class_java.lang.Object"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#EEEEFF" CLASS="TableSubHeadingColor"><TH ALIGN="left"><B>从类 java.lang.<A HREF="../Object.html" title="java.lang 中的类">Object</A> 继承的方法</B></TH></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><A HREF="../Object.html#clone()">clone</A>, <A HREF="../Object.html#equals(java.lang.Object)">equals</A>, <A HREF="../Object.html#finalize()">finalize</A>, <A HREF="../Object.html#getClass()">getClass</A>, <A HREF="../Object.html#hashCode()">hashCode</A>, <A HREF="../Object.html#notify()">notify</A>, <A HREF="../Object.html#notifyAll()">notifyAll</A>, <A HREF="../Object.html#toString()">toString</A>, <A HREF="../Object.html#wait()">wait</A>, <A HREF="../Object.html#wait(long)">wait</A>, <A HREF="../Object.html#wait(long, int)">wait</A></CODE></TD></TR></TABLE>&nbsp;<P><!-- ============ METHOD DETAIL ========== --><A NAME="method_detail"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TH ALIGN="left" COLSPAN="1"><FONT SIZE="+2"><B>方法详细信息</B></FONT></TH></TR></TABLE><A NAME="get()"><!-- --></A><H3>get</H3><PRE>public <A HREF="Reference.html" title="Reference 中的类型参数">T</A> <B>get</B>()</PRE><DL><DD>返回此引用对象的指示对象。如果此引用对象已经由程序或垃圾回收器清除,则此方法将返回 <code>null</code>。<P><DD><DL><DT><B>返回:</B><DD>此引用所引用的对象;如果此引用对象已经清除,则返回 <code>null</code>。</DL></DD></DL><HR><A NAME="clear()"><!-- --></A><H3>clear</H3><PRE>public void <B>clear</B>()</PRE><DL><DD>清除此引用对象。调用此方法不会导致对象被加入队列。<P><DD><DL></DL></DD></DL><HR><A NAME="isEnqueued()"><!-- --></A><H3>isEnqueued</H3><PRE>public boolean <B>isEnqueued</B>()</PRE><DL><DD>由程序或垃圾回收器通知是否已将此引用对象加入队列。如果创建此引用对象时没有向队列注册它,则该方法将总是返回 <code>false</code>。<P><DD><DL><DT><B>返回:</B><DD>当且仅当此引用对象已经加入队列时返回 <code>true</code></DL></DD></DL><HR><A NAME="enqueue()"><!-- --></A><H3>enqueue</H3><PRE>public boolean <B>enqueue</B>()</PRE><DL><DD>将此引用对象添加到引用对象已向其注册的队列(如果有)。<P><DD><DL><DT><B>返回:</B><DD>如果成功将此引用对象加入队列中,则返回 <code>true</code>;如果它已经加入队列或者在创建时没有在队列中注册它,则返回 <code>false</code>。</DL></DD></DL><!-- ========= END OF CLASS DATA ========= --><HR><!-- ======= START OF BOTTOM NAVBAR ====== --><A NAME="navbar_bottom"><!-- --></A><A HREF="#skip-navbar_bottom" title="跳过导航链接"></A><TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0" SUMMARY=""><TR><TD COLSPAN=2 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"><A NAME="navbar_bottom_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>概述</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="package-summary.html"><FONT CLASS="NavBarFont1"><B>软件包</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> &nbsp;<FONT CLASS="NavBarFont1Rev"><B>类</B></FONT>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="class-use/Reference.html"><FONT CLASS="NavBarFont1"><B>使用</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>树</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="../../../deprecated-list.html"><FONT CLASS="NavBarFont1"><B>已过时</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="../../../index-files/index-1.html"><FONT CLASS="NavBarFont1"><B>索引</B></FONT></A>&nbsp;</TD>  <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1">    <A HREF="../../../help-doc.html"><FONT CLASS="NavBarFont1"><B>帮助</B></FONT></A>&nbsp;</TD>  </TR></TABLE></TD><TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM><b>Java<sup><font size=-2>TM</font></sup>&nbsp;2&nbsp;Platform<br>Standard&nbsp;Ed. 5.0</b></EM></TD></TR><TR><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2">&nbsp;<A HREF="PhantomReference.html" title="java.lang.ref 中的类"><B>上一个类</B></A>&nbsp;&nbsp;<A HREF="ReferenceQueue.html" title="java.lang.ref 中的类"><B>下一个类</B></A></FONT></TD><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2">  <A HREF="../../../index.html@java_2Flang_2Fref_2FReference.html" target="_top"><B>框架</B></A>  &nbsp;&nbsp;<A HREF="Reference.html" target="_top"><B>无框架</B></A>  &nbsp;&nbsp;<SCRIPT type="text/javascript">  <!--  if(window==top) {    document.writeln('<A HREF="../../../allclasses-noframe.html"><B>所有类</B></A>');  }  //--></SCRIPT><NOSCRIPT>  <A HREF="../../../allclasses-noframe.html"><B>所有类</B></A></NOSCRIPT></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">  摘要:&nbsp;嵌套&nbsp;|&nbsp;字段&nbsp;|&nbsp;构造方法&nbsp;|&nbsp;<A HREF="#method_summary">方法</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">详细信息:&nbsp;字段&nbsp;|&nbsp;构造方法&nbsp;|&nbsp;<A HREF="#method_detail">方法</A></FONT></TD></TR></TABLE><A NAME="skip-navbar_bottom"></A><!-- ======== END OF BOTTOM NAVBAR ======= --><HR><font size="-1"><a href="../../../../../../../../../java.sun.com/cgi-bin/bugreport.cgi">提交错误或意见</a><br>有关更多的 API 参考资料和开发人员文档,请参阅 <a href="../../../../../../../../../java.sun.com/j2se/1.5.0/docs/relnotes/devdocs-vs-specs.html">Java 2 SDK SE 开发人员文档</a>。该文档包含更详细的、面向开发人员的描述,以及总体概述、术语定义、使用技巧和工作代码示例。 <p>版权所有 2004 Sun Microsystems, Inc. 保留所有权利。 请遵守<a href="../../../../../../../../../java.sun.com/j2se/1.5.0/docs/relnotes/license.html">许可证条款</a>。另请参阅<a href="../../../../../../../../../java.sun.com/docs/redist.html">文档重新分发政策</a>。</font></BODY></HTML>

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