diff -r 000000000000 -r 959103a6100f src/share/classes/com/sun/source/util/TreeScanner.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/classes/com/sun/source/util/TreeScanner.java	Wed Apr 27 01:34:52 2016 +0800
@@ -0,0 +1,418 @@
+/*
+ * Copyright (c) 2005, 2013, 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.source.util;
+
+import com.sun.source.tree.*;
+
+/**
+ * A TreeVisitor that visits all the child tree nodes.
+ * To visit nodes of a particular type, just override the
+ * corresponding visitXYZ method.
+ * Inside your method, call super.visitXYZ to visit descendant
+ * nodes.
+ *
+ * <p>The default implementation of the visitXYZ methods will determine
+ * a result as follows:
+ * <ul>
+ * <li>If the node being visited has no children, the result will be null.
+ * <li>If the node being visited has one child, the result will be the
+ * result of calling {@code scan} on that child. The child may be a simple node
+ * or itself a list of nodes.
+ * <li> If the node being visited has more than one child, the result will
+ * be determined by calling {@code scan} each child in turn, and then combining the
+ * result of each scan after the first with the cumulative result
+ * so far, as determined by the {@link #reduce} method. Each child may be either
+ * a simple node of a list of nodes. The default behavior of the {@code reduce}
+ * method is such that the result of the visitXYZ method will be the result of
+ * the last child scanned.
+ * </ul>
+ *
+ * <p>Here is an example to count the number of identifier nodes in a tree:
+ * <pre>
+ *   class CountIdentifiers extends TreeScanner&lt;Integer,Void&gt; {
+ *      {@literal @}Override
+ *      public Integer visitIdentifier(IdentifierTree node, Void p) {
+ *          return 1;
+ *      }
+ *      {@literal @}Override
+ *      public Integer reduce(Integer r1, Integer r2) {
+ *          return (r1 == null ? 0 : r1) + (r2 == null ? 0 : r2);
+ *      }
+ *   }
+ * </pre>
+ *
+ * @author Peter von der Ah&eacute;
+ * @author Jonathan Gibbons
+ * @since 1.6
+ */
+@jdk.Exported
+public class TreeScanner<R,P> implements TreeVisitor<R,P> {
+
+    /** Scan a single node.
+     */
+    public R scan(Tree node, P p) {
+        return (node == null) ? null : node.accept(this, p);
+    }
+
+    private R scanAndReduce(Tree node, P p, R r) {
+        return reduce(scan(node, p), r);
+    }
+
+    /** Scan a list of nodes.
+     */
+    public R scan(Iterable<? extends Tree> nodes, P p) {
+        R r = null;
+        if (nodes != null) {
+            boolean first = true;
+            for (Tree node : nodes) {
+                r = (first ? scan(node, p) : scanAndReduce(node, p, r));
+                first = false;
+            }
+        }
+        return r;
+    }
+
+    private R scanAndReduce(Iterable<? extends Tree> nodes, P p, R r) {
+        return reduce(scan(nodes, p), r);
+    }
+
+    /**
+     * Reduces two results into a combined result.
+     * The default implementation is to return the first parameter.
+     * The general contract of the method is that it may take any action whatsoever.
+     */
+    public R reduce(R r1, R r2) {
+        return r1;
+    }
+
+
+/* ***************************************************************************
+ * Visitor methods
+ ****************************************************************************/
+
+    public R visitCompilationUnit(CompilationUnitTree node, P p) {
+        R r = scan(node.getPackageAnnotations(), p);
+        r = scanAndReduce(node.getPackageName(), p, r);
+        r = scanAndReduce(node.getImports(), p, r);
+        r = scanAndReduce(node.getTypeDecls(), p, r);
+        return r;
+    }
+
+    public R visitImport(ImportTree node, P p) {
+        return scan(node.getQualifiedIdentifier(), p);
+    }
+
+    public R visitClass(ClassTree node, P p) {
+        R r = scan(node.getModifiers(), p);
+        r = scanAndReduce(node.getTypeParameters(), p, r);
+        r = scanAndReduce(node.getExtendsClause(), p, r);
+        r = scanAndReduce(node.getImplementsClause(), p, r);
+        r = scanAndReduce(node.getMembers(), p, r);
+        return r;
+    }
+
+    public R visitMethod(MethodTree node, P p) {
+        R r = scan(node.getModifiers(), p);
+        r = scanAndReduce(node.getReturnType(), p, r);
+        r = scanAndReduce(node.getTypeParameters(), p, r);
+        r = scanAndReduce(node.getParameters(), p, r);
+        r = scanAndReduce(node.getReceiverParameter(), p, r);
+        r = scanAndReduce(node.getThrows(), p, r);
+        r = scanAndReduce(node.getBody(), p, r);
+        r = scanAndReduce(node.getDefaultValue(), p, r);
+        return r;
+    }
+
+    public R visitVariable(VariableTree node, P p) {
+        R r = scan(node.getModifiers(), p);
+        r = scanAndReduce(node.getType(), p, r);
+        r = scanAndReduce(node.getNameExpression(), p, r);
+        r = scanAndReduce(node.getInitializer(), p, r);
+        return r;
+    }
+
+    public R visitEmptyStatement(EmptyStatementTree node, P p) {
+        return null;
+    }
+
+    public R visitBlock(BlockTree node, P p) {
+        return scan(node.getStatements(), p);
+    }
+
+    public R visitDoWhileLoop(DoWhileLoopTree node, P p) {
+        R r = scan(node.getStatement(), p);
+        r = scanAndReduce(node.getCondition(), p, r);
+        return r;
+    }
+
+    public R visitWhileLoop(WhileLoopTree node, P p) {
+        R r = scan(node.getCondition(), p);
+        r = scanAndReduce(node.getStatement(), p, r);
+        return r;
+    }
+
+    public R visitForLoop(ForLoopTree node, P p) {
+        R r = scan(node.getInitializer(), p);
+        r = scanAndReduce(node.getCondition(), p, r);
+        r = scanAndReduce(node.getUpdate(), p, r);
+        r = scanAndReduce(node.getStatement(), p, r);
+        return r;
+    }
+
+    public R visitEnhancedForLoop(EnhancedForLoopTree node, P p) {
+        R r = scan(node.getVariable(), p);
+        r = scanAndReduce(node.getExpression(), p, r);
+        r = scanAndReduce(node.getStatement(), p, r);
+        return r;
+    }
+
+    public R visitLabeledStatement(LabeledStatementTree node, P p) {
+        return scan(node.getStatement(), p);
+    }
+
+    public R visitSwitch(SwitchTree node, P p) {
+        R r = scan(node.getExpression(), p);
+        r = scanAndReduce(node.getCases(), p, r);
+        return r;
+    }
+
+    public R visitCase(CaseTree node, P p) {
+        R r = scan(node.getExpression(), p);
+        r = scanAndReduce(node.getStatements(), p, r);
+        return r;
+    }
+
+    public R visitSynchronized(SynchronizedTree node, P p) {
+        R r = scan(node.getExpression(), p);
+        r = scanAndReduce(node.getBlock(), p, r);
+        return r;
+    }
+
+    public R visitTry(TryTree node, P p) {
+        R r = scan(node.getResources(), p);
+        r = scanAndReduce(node.getBlock(), p, r);
+        r = scanAndReduce(node.getCatches(), p, r);
+        r = scanAndReduce(node.getFinallyBlock(), p, r);
+        return r;
+    }
+
+    public R visitCatch(CatchTree node, P p) {
+        R r = scan(node.getParameter(), p);
+        r = scanAndReduce(node.getBlock(), p, r);
+        return r;
+    }
+
+    public R visitConditionalExpression(ConditionalExpressionTree node, P p) {
+        R r = scan(node.getCondition(), p);
+        r = scanAndReduce(node.getTrueExpression(), p, r);
+        r = scanAndReduce(node.getFalseExpression(), p, r);
+        return r;
+    }
+
+    public R visitIf(IfTree node, P p) {
+        R r = scan(node.getCondition(), p);
+        r = scanAndReduce(node.getThenStatement(), p, r);
+        r = scanAndReduce(node.getElseStatement(), p, r);
+        return r;
+    }
+
+    public R visitExpressionStatement(ExpressionStatementTree node, P p) {
+        return scan(node.getExpression(), p);
+    }
+
+    public R visitBreak(BreakTree node, P p) {
+        return null;
+    }
+
+    public R visitContinue(ContinueTree node, P p) {
+        return null;
+    }
+
+    public R visitReturn(ReturnTree node, P p) {
+        return scan(node.getExpression(), p);
+    }
+
+    public R visitThrow(ThrowTree node, P p) {
+        return scan(node.getExpression(), p);
+    }
+
+    public R visitAssert(AssertTree node, P p) {
+        R r = scan(node.getCondition(), p);
+        r = scanAndReduce(node.getDetail(), p, r);
+        return r;
+    }
+
+    public R visitMethodInvocation(MethodInvocationTree node, P p) {
+        R r = scan(node.getTypeArguments(), p);
+        r = scanAndReduce(node.getMethodSelect(), p, r);
+        r = scanAndReduce(node.getArguments(), p, r);
+        return r;
+    }
+
+    public R visitNewClass(NewClassTree node, P p) {
+        R r = scan(node.getEnclosingExpression(), p);
+        r = scanAndReduce(node.getIdentifier(), p, r);
+        r = scanAndReduce(node.getTypeArguments(), p, r);
+        r = scanAndReduce(node.getArguments(), p, r);
+        r = scanAndReduce(node.getClassBody(), p, r);
+        return r;
+    }
+
+    public R visitNewArray(NewArrayTree node, P p) {
+        R r = scan(node.getType(), p);
+        r = scanAndReduce(node.getDimensions(), p, r);
+        r = scanAndReduce(node.getInitializers(), p, r);
+        r = scanAndReduce(node.getAnnotations(), p, r);
+        for (Iterable< ? extends Tree> dimAnno : node.getDimAnnotations()) {
+            r = scanAndReduce(dimAnno, p, r);
+        }
+        return r;
+    }
+
+    public R visitLambdaExpression(LambdaExpressionTree node, P p) {
+        R r = scan(node.getParameters(), p);
+        r = scanAndReduce(node.getBody(), p, r);
+        return r;
+    }
+
+    public R visitParenthesized(ParenthesizedTree node, P p) {
+        return scan(node.getExpression(), p);
+    }
+
+    public R visitAssignment(AssignmentTree node, P p) {
+        R r = scan(node.getVariable(), p);
+        r = scanAndReduce(node.getExpression(), p, r);
+        return r;
+    }
+
+    public R visitCompoundAssignment(CompoundAssignmentTree node, P p) {
+        R r = scan(node.getVariable(), p);
+        r = scanAndReduce(node.getExpression(), p, r);
+        return r;
+    }
+
+    public R visitUnary(UnaryTree node, P p) {
+        return scan(node.getExpression(), p);
+    }
+
+    public R visitBinary(BinaryTree node, P p) {
+        R r = scan(node.getLeftOperand(), p);
+        r = scanAndReduce(node.getRightOperand(), p, r);
+        return r;
+    }
+
+    public R visitTypeCast(TypeCastTree node, P p) {
+        R r = scan(node.getType(), p);
+        r = scanAndReduce(node.getExpression(), p, r);
+        return r;
+    }
+
+    public R visitInstanceOf(InstanceOfTree node, P p) {
+        R r = scan(node.getExpression(), p);
+        r = scanAndReduce(node.getType(), p, r);
+        return r;
+    }
+
+    public R visitArrayAccess(ArrayAccessTree node, P p) {
+        R r = scan(node.getExpression(), p);
+        r = scanAndReduce(node.getIndex(), p, r);
+        return r;
+    }
+
+    public R visitMemberSelect(MemberSelectTree node, P p) {
+        return scan(node.getExpression(), p);
+    }
+
+    public R visitMemberReference(MemberReferenceTree node, P p) {
+        R r = scan(node.getQualifierExpression(), p);
+        r = scanAndReduce(node.getTypeArguments(), p, r);
+        return r;
+    }
+
+    public R visitIdentifier(IdentifierTree node, P p) {
+        return null;
+    }
+
+    public R visitLiteral(LiteralTree node, P p) {
+        return null;
+    }
+
+    public R visitPrimitiveType(PrimitiveTypeTree node, P p) {
+        return null;
+    }
+
+    public R visitArrayType(ArrayTypeTree node, P p) {
+        return scan(node.getType(), p);
+    }
+
+    public R visitParameterizedType(ParameterizedTypeTree node, P p) {
+        R r = scan(node.getType(), p);
+        r = scanAndReduce(node.getTypeArguments(), p, r);
+        return r;
+    }
+
+    public R visitUnionType(UnionTypeTree node, P p) {
+        return scan(node.getTypeAlternatives(), p);
+    }
+
+    public R visitIntersectionType(IntersectionTypeTree node, P p) {
+        return scan(node.getBounds(), p);
+    }
+
+    public R visitTypeParameter(TypeParameterTree node, P p) {
+        R r = scan(node.getAnnotations(), p);
+        r = scanAndReduce(node.getBounds(), p, r);
+        return r;
+    }
+
+    public R visitWildcard(WildcardTree node, P p) {
+        return scan(node.getBound(), p);
+    }
+
+    public R visitModifiers(ModifiersTree node, P p) {
+        return scan(node.getAnnotations(), p);
+    }
+
+    public R visitAnnotation(AnnotationTree node, P p) {
+        R r = scan(node.getAnnotationType(), p);
+        r = scanAndReduce(node.getArguments(), p, r);
+        return r;
+    }
+
+   public R visitAnnotatedType(AnnotatedTypeTree node, P p) {
+       R r = scan(node.getAnnotations(), p);
+       r = scanAndReduce(node.getUnderlyingType(), p, r);
+       return r;
+   }
+
+    public R visitOther(Tree node, P p) {
+        return null;
+    }
+
+    public R visitErroneous(ErroneousTree node, P p) {
+        return null;
+    }
+}