feat(jdk8): move files to new folder to avoid resources compiled.

jdkSrc/jdk8/com/sun/jmx/mbeanserver/WeakIdentityHashMap.java

@@ -0,0 +1,137 @@
+/*
+ * Copyright (c) 2005, 2008, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package com.sun.jmx.mbeanserver;
+
+import static com.sun.jmx.mbeanserver.Util.*;
+
+import java.lang.ref.Reference;
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.WeakReference;
+
+import java.util.Map;
+
+
+/**
+ * <p>A map where keys are compared using identity comparison (like
+ * IdentityHashMap) but where the presence of an object as a key in
+ * the map does not prevent it being garbage collected (like
+ * WeakHashMap).  This class does not implement the Map interface
+ * because it is difficult to ensure correct semantics for iterators
+ * over the entrySet().</p>
+ *
+ * <p>Because we do not implement Map, we do not copy the questionable
+ * interface where you can call get(k) or remove(k) for any type of k,
+ * which of course can only have an effect if k is of type K.</p>
+ *
+ * <p>This map does not support null keys.</p>
+ */
+/*
+ * The approach
+ * is to wrap each key in a WeakReference and use the wrapped value as
+ * a key in an ordinary HashMap.  The WeakReference has to be a
+ * subclass IdentityWeakReference (IWR) where two IWRs are equal if
+ * they refer to the same object.  This enables us to find the entry
+ * again.
+ */
+class WeakIdentityHashMap<K, V> {
+    private WeakIdentityHashMap() {}
+
+    static <K, V> WeakIdentityHashMap<K, V> make() {
+        return new WeakIdentityHashMap<K, V>();
+    }
+
+    V get(K key) {
+        expunge();
+        WeakReference<K> keyref = makeReference(key);
+        return map.get(keyref);
+    }
+
+    public V put(K key, V value) {
+        expunge();
+        if (key == null)
+            throw new IllegalArgumentException("Null key");
+        WeakReference<K> keyref = makeReference(key, refQueue);
+        return map.put(keyref, value);
+    }
+
+    public V remove(K key) {
+        expunge();
+        WeakReference<K> keyref = makeReference(key);
+        return map.remove(keyref);
+    }
+
+    private void expunge() {
+        Reference<? extends K> ref;
+        while ((ref = refQueue.poll()) != null)
+            map.remove(ref);
+    }
+
+    private WeakReference<K> makeReference(K referent) {
+        return new IdentityWeakReference<K>(referent);
+    }
+
+    private WeakReference<K> makeReference(K referent, ReferenceQueue<K> q) {
+        return new IdentityWeakReference<K>(referent, q);
+    }
+
+    /**
+     * WeakReference where equals and hashCode are based on the
+     * referent.  More precisely, two objects are equal if they are
+     * identical or if they both have the same non-null referent.  The
+     * hashCode is the value the original referent had.  Even if the
+     * referent is cleared, the hashCode remains.  Thus, objects of
+     * this class can be used as keys in hash-based maps and sets.
+     */
+    private static class IdentityWeakReference<T> extends WeakReference<T> {
+        IdentityWeakReference(T o) {
+            this(o, null);
+        }
+
+        IdentityWeakReference(T o, ReferenceQueue<T> q) {
+            super(o, q);
+            this.hashCode = (o == null) ? 0 : System.identityHashCode(o);
+        }
+
+        public boolean equals(Object o) {
+            if (this == o)
+                return true;
+            if (!(o instanceof IdentityWeakReference<?>))
+                return false;
+            IdentityWeakReference<?> wr = (IdentityWeakReference<?>) o;
+            Object got = get();
+            return (got != null && got == wr.get());
+        }
+
+        public int hashCode() {
+            return hashCode;
+        }
+
+        private final int hashCode;
+    }
+
+    private Map<WeakReference<K>, V> map = newMap();
+    private ReferenceQueue<K> refQueue = new ReferenceQueue<K>();
+}