--- /dev/null	2018-06-17 23:18:20.806999507 +0800
+++ new/src/share/classes/jdk/jfr/consumer/LongMap.java	2019-01-29 10:59:05.291563235 +0800
@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2016, 2019, 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 jdk.jfr.consumer;
+
+import java.util.HashMap;
+import java.util.Iterator;
+
+/**
+ * Commonly used data structure for looking up objects given an id (long value)
+ *
+ * TODO: Implement without using Map and Long objects, to minimize allocation
+ *
+ * @param <T>
+ */
+final class LongMap<T> implements Iterable<T> {
+    private final HashMap<Long, T> map;
+
+    LongMap() {
+        map = new HashMap<>(101);
+    }
+
+    void put(long id, T object) {
+        map.put(id, object);
+    }
+
+    T get(long id) {
+        return map.get(id);
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+        return map.values().iterator();
+    }
+
+    Iterator<Long> keys() {
+        return map.keySet().iterator();
+    }
+}