--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/vmTestbase/gc/g1/unloading/bytecode/GenClassesBuilder.java	Thu May 17 14:52:47 2018 -0700
@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2017, 2018, 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.
+ *
+ * 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 gc.g1.unloading.bytecode;
+
+import jdk.test.lib.JDKToolLauncher;
+import jdk.test.lib.Utils;
+import jdk.test.lib.process.ProcessTools;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.stream.Stream;
+
+/**
+ * Uses {@link gc.g1.unloading.bytecode.HumongousTemplateClassGen} to generate
+ * source code of HumongousTemplateClass and compiles it to {@code test.classes}.
+ */
+public class GenClassesBuilder {
+    public static void main(String[] args) {
+        Path genSrc = Paths.get("genSrc").toAbsolutePath();
+        Path classesDir = Paths.get(Utils.TEST_CLASSES).toAbsolutePath();
+        generateSource(genSrc);
+        compileSource(genSrc, classesDir);
+    }
+
+    private static void compileSource(Path srcDst, Path classesDir) {
+        JDKToolLauncher javac = JDKToolLauncher.create("javac")
+                                               .addToolArg("-d")
+                                               .addToolArg(classesDir.toString())
+                                               .addToolArg("-cp")
+                                               .addToolArg(Utils.TEST_CLASS_PATH);
+        try (Stream<Path> stream = Files.walk(srcDst)) {
+            stream.map(Path::toAbsolutePath)
+                  .map(Path::toString)
+                  .filter(s -> s.endsWith(".java"))
+                  .forEach(javac::addToolArg);
+        } catch (IOException e) {
+            throw new Error("traverse source dir " + srcDst, e);
+        }
+        String[] command = javac.getCommand();
+        try {
+            ProcessTools.executeCommand(command)
+                        .shouldHaveExitValue(0);
+        } catch (Error | RuntimeException e) {
+            throw e;
+        } catch (Throwable e) {
+            throw new Error("execution of javac(" + Arrays.toString(command) + ") failed", e);
+        }
+    }
+
+    private static void generateSource(Path dir) {
+        try {
+            Files.createDirectories(dir);
+        } catch (IOException e) {
+            throw new Error("can't create dirs for" + dir, e);
+        }
+
+        try {
+            HumongousTemplateClassGen.main(new String[]{dir.toString()});
+        } catch (Exception e) {
+            throw new Error("can't generate classes", e);
+        }
+    }
+}
+