diff -r 1c96344ecd49 -r 65ec6de1d6b4 langtools/src/jdk.jshell/share/classes/jdk/jshell/ClassTracker.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/src/jdk.jshell/share/classes/jdk/jshell/ClassTracker.java	Mon Oct 19 19:15:16 2015 +0200
@@ -0,0 +1,97 @@
+/*
+ * 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 jdk.jshell;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import com.sun.jdi.ReferenceType;
+
+/**
+ * Tracks the state of a class through compilation and loading in the remote
+ * environment.
+ *
+ * @author Robert Field
+ */
+class ClassTracker {
+
+    private final JShell state;
+    private final HashMap<String, ClassInfo> map;
+
+    ClassTracker(JShell state) {
+        this.state = state;
+        this.map = new HashMap<>();
+    }
+
+    class ClassInfo {
+
+        private final String className;
+        private byte[] bytes;
+        private byte[] loadedBytes;
+        private ReferenceType rt;
+
+        private ClassInfo(String className) {
+            this.className = className;
+        }
+
+        String getClassName() {
+            return className;
+        }
+
+        byte[] getBytes() {
+            return bytes;
+        }
+
+        void setBytes(byte[] bytes) {
+            this.bytes = bytes;
+        }
+
+        void setLoaded() {
+            loadedBytes = bytes;
+        }
+
+        boolean isLoaded() {
+            return Arrays.equals(loadedBytes, bytes);
+        }
+
+        ReferenceType getReferenceTypeOrNull() {
+            if (rt == null) {
+                rt = state.executionControl().nameToRef(className);
+            }
+            return rt;
+        }
+    }
+
+    ClassInfo classInfo(String className, byte[] bytes) {
+        ClassInfo ci = map.computeIfAbsent(className, k -> new ClassInfo(k));
+        ci.setBytes(bytes);
+        return ci;
+    }
+
+    ClassInfo get(String className) {
+        return map.get(className);
+    }
+
+}