diff -r 000000000000 -r 959103a6100f src/share/classes/com/sun/tools/javac/util/Assert.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/classes/com/sun/tools/javac/util/Assert.java	Wed Apr 27 01:34:52 2016 +0800
@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2011, 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.tools.javac.util;
+
+
+/**
+ * Simple facility for unconditional assertions.
+ * The methods in this class are described in terms of equivalent assert
+ * statements, assuming that assertions have been enabled.
+ *
+ *  <p><b>This is NOT part of any supported API.
+ *  If you write code that depends on this, you do so at your own risk.
+ *  This code and its internal interfaces are subject to change or
+ *  deletion without notice.</b>
+ */
+public class Assert {
+    /** Equivalent to
+     *   assert cond;
+     */
+    public static void check(boolean cond) {
+        if (!cond)
+            error();
+    }
+
+    /** Equivalent to
+     *   assert (o == null);
+     */
+    public static void checkNull(Object o) {
+        if (o != null)
+            error();
+    }
+
+    /** Equivalent to
+     *   assert (t != null); return t;
+     */
+    public static <T> T checkNonNull(T t) {
+        if (t == null)
+            error();
+        return t;
+    }
+
+    /** Equivalent to
+     *   assert cond : value;
+     */
+    public static void check(boolean cond, int value) {
+        if (!cond)
+            error(String.valueOf(value));
+    }
+
+    /** Equivalent to
+     *   assert cond : value;
+     */
+    public static void check(boolean cond, long value) {
+        if (!cond)
+            error(String.valueOf(value));
+    }
+
+    /** Equivalent to
+     *   assert cond : value;
+     */
+    public static void check(boolean cond, Object value) {
+        if (!cond)
+            error(String.valueOf(value));
+    }
+
+    /** Equivalent to
+     *   assert cond : value;
+     */
+    public static void check(boolean cond, String msg) {
+        if (!cond)
+            error(msg);
+    }
+
+    /** Equivalent to
+     *   assert (o == null) : value;
+     */
+    public static void checkNull(Object o, Object value) {
+        if (o != null)
+            error(String.valueOf(value));
+    }
+
+    /** Equivalent to
+     *   assert (o == null) : value;
+     */
+    public static void checkNull(Object o, String msg) {
+        if (o != null)
+            error(msg);
+    }
+
+    /** Equivalent to
+     *   assert (o != null) : value;
+     */
+    public static <T> T checkNonNull(T t, String msg) {
+        if (t == null)
+            error(msg);
+        return t;
+    }
+
+    /** Equivalent to
+     *   assert false;
+     */
+    public static void error() {
+        throw new AssertionError();
+    }
+
+    /** Equivalent to
+     *   assert false : msg;
+     */
+    public static void error(String msg) {
+        throw new AssertionError(msg);
+    }
+
+    /** Prevent instantiation. */
+    private Assert() { }
+}