8187443: Forest Consolidation: Move files to unified layout

Reviewed-by: darcy, ihse

src/java.base/share/classes/java/lang/ref/FinalizerHistogram.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2015, 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 java.lang.ref;
+
+
+import java.util.Map;
+import java.util.HashMap;
+import java.util.Arrays;
+import java.util.Comparator;
+
+/**
+ * This FinalizerHistogram class is for GC.finalizer_info diagnostic command support.
+ * It is invoked by the VM.
+ */
+
+final class FinalizerHistogram {
+
+    private static final class Entry {
+        private int instanceCount;
+        private final String className;
+
+        int getInstanceCount() {
+            return instanceCount;
+        }
+
+        void increment() {
+            instanceCount += 1;
+        }
+
+        Entry(String className) {
+            this.className = className;
+        }
+    }
+
+    // Method below is called by VM and VM expect certain
+    // entry class layout.
+
+    static Entry[] getFinalizerHistogram() {
+        Map<String, Entry> countMap = new HashMap<>();
+        ReferenceQueue<Object> queue = Finalizer.getQueue();
+        queue.forEach(r -> {
+            Object referent = r.get();
+            if (referent != null) {
+                countMap.computeIfAbsent(
+                    referent.getClass().getName(), Entry::new).increment();
+                /* Clear stack slot containing this variable, to decrease
+                   the chances of false retention with a conservative GC */
+                referent = null;
+            }
+        });
+
+        Entry fhe[] = countMap.values().toArray(new Entry[countMap.size()]);
+        Arrays.sort(fhe,
+                Comparator.comparingInt(Entry::getInstanceCount).reversed());
+        return fhe;
+    }
+}