From 56a71a00760feb71ae4a9e96ca5ae94c9314a795 Mon Sep 17 00:00:00 2001
From: Steve Loughran <stevel@apache.org>
Date: Tue, 10 Sep 2002 22:19:28 +0000
Subject: [PATCH] a reference that is hard on 1.1, weak on 1.2+

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@273319 13f79535-47bb-0310-9956-ffa450edef68
---
 .../tools/ant/util/WeakishReference.java      | 134 ++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 src/main/org/apache/tools/ant/util/WeakishReference.java

diff --git a/src/main/org/apache/tools/ant/util/WeakishReference.java b/src/main/org/apache/tools/ant/util/WeakishReference.java
new file mode 100644
index 000000000..e12a7b9f6
--- /dev/null
+++ b/src/main/org/apache/tools/ant/util/WeakishReference.java
@@ -0,0 +1,134 @@
+/*
+ *  The Apache Software License, Version 1.1
+ *
+ *  Copyright (c) 2002 The Apache Software Foundation.  All rights
+ *  reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions
+ *  are met:
+ *
+ *  1. Redistributions of source code must retain the above copyright
+ *  notice, this list of conditions and the following disclaimer.
+ *
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *  notice, this list of conditions and the following disclaimer in
+ *  the documentation and/or other materials provided with the
+ *  distribution.
+ *
+ *  3. The end-user documentation included with the redistribution, if
+ *  any, must include the following acknowlegement:
+ *  "This product includes software developed by the
+ *  Apache Software Foundation (http://www.apache.org/)."
+ *  Alternately, this acknowlegement may appear in the software itself,
+ *  if and wherever such third-party acknowlegements normally appear.
+ *
+ *  4. The names "The Jakarta Project", "Ant", and "Apache Software
+ *  Foundation" must not be used to endorse or promote products derived
+ *  from this software without prior written permission. For written
+ *  permission, please contact apache@apache.org.
+ *
+ *  5. Products derived from this software may not be called "Apache"
+ *  nor may "Apache" appear in their names without prior written
+ *  permission of the Apache Group.
+ *
+ *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ *  DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ *  ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ *  USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ *  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ *  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ *  OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ *  SUCH DAMAGE.
+ *  ====================================================================
+ *
+ *  This software consists of voluntary contributions made by many
+ *  individuals on behalf of the Apache Software Foundation.  For more
+ *  information on the Apache Software Foundation, please see
+ *  <http://www.apache.org/>.
+ */
+
+package org.apache.tools.ant.util;
+
+import java.lang.ref.WeakReference;
+
+/**
+ * this is a weak reference on java1.2 and up, a hard
+ * reference on java1.1
+ * @since ant1.6
+ */
+public abstract class WeakishReference  {
+
+
+    /**
+     * create the appropriate type of reference for the java version
+     * @param object
+     * @return
+     */
+    public static WeakishReference createReference(Object object) {
+        if(JavaEnvUtils.isJavaVersion(JavaEnvUtils.JAVA_1_1)) {
+            return new HardReference(object);
+        } else {
+            return new SoftReference(object);
+        }
+    }
+
+    /**
+     * Returns this reference object's referent.  If this reference object has
+     * been cleared, then this method returns <code>null</code>.
+     *
+     * @return	 The object to which this reference refers, or
+     *		 <code>null</code> if this reference object has been cleared
+     */
+    public abstract Object get();
+
+    /**
+     * A hard reference for Java 1.1
+     */
+    private static class HardReference extends WeakishReference {
+        private Object object;
+
+        /**
+         * construct
+         * @param object
+         */
+        public HardReference(Object object) {
+            this.object = object;
+        }
+
+        /**
+         * Returns this reference object's referent.
+         */
+        public Object get() {
+            return object;
+        }
+    }
+
+    /**
+     * a soft reference for Java 1.2 or later
+     */
+    private static class SoftReference extends WeakishReference {
+        private WeakReference weakref;
+
+        /**
+         * create a new soft reference, which is bound to a
+         * Weak reference inside
+         * @param reference
+         * @see java.lang.ref.WeakReference
+         */
+        public SoftReference(Object reference) {
+            this.weakref = new WeakReference(reference);
+        }
+
+        /**
+         * Returns this reference object's referent.
+         */
+        public Object get() {
+            return weakref.get();
+        }
+    }
+}