1 /*
   2  * Copyright (c) 1995, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package sun.applet;
  27 
  28 import java.awt.Toolkit;
  29 import java.awt.Image;
  30 import java.lang.ref.SoftReference;
  31 import sun.awt.image.URLImageSource;
  32 import java.net.URL;
  33 
  34 @Deprecated(since = "9")
  35 class AppletImageRef {
  36     private SoftReference<Image> soft = null;
  37 
  38     URL url;
  39 
  40     /**
  41      * Returns a pointer to the object referenced by this Ref.  If the object
  42      * has been thrown away by the garbage collector, it will be
  43      * reconstituted. This method does everything necessary to ensure that the garbage
  44      * collector throws things away in Least Recently Used(LRU) order.  Applications should
  45      * never override this method. The get() method effectively caches calls to
  46      * reconstitute().
  47      */
  48     public synchronized Image get() {
  49         Image t = check();
  50         if (t == null) {
  51             t = reconstitute();
  52             setThing(t);
  53         }
  54         return t;
  55     }
  56 
  57     /**
  58      * Create the Ref
  59      */
  60     AppletImageRef(URL url) {
  61         this.url = url;
  62     }
  63 
  64     /**
  65      * Flushes the cached object.  Forces the next invocation of get() to
  66      * invoke reconstitute().
  67      */
  68     public synchronized void flush() {
  69         SoftReference<Image> s = soft;
  70         if (s != null) s.clear();
  71         soft = null;
  72     }
  73 
  74     /**
  75      * Sets the thing to the specified object.
  76      * @param thing the specified object
  77      */
  78     public synchronized void setThing(Image thing) {
  79         flush();
  80         soft = new SoftReference<>(thing);
  81     }
  82 
  83     /**
  84      * Checks to see what object is being pointed at by this Ref and returns it.
  85      */
  86     public synchronized Image check() {
  87         SoftReference<Image> s = soft;
  88         if (s == null) return null;
  89         return s.get();
  90     }
  91 
  92     /**
  93      * Reconsitute the image.  Only called when the ref has been flushed.
  94      */
  95     public Image reconstitute() {
  96         Image img = Toolkit.getDefaultToolkit().createImage(new URLImageSource(url));
  97         return img;
  98     }
  99 }