TreePathScanner.java revision 3193:3b3bea483542 
1/*
2 * Copyright (c) 2006, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package com.sun.source.util;
27
28import com.sun.source.tree.*;
29
30/**
31 * A TreeVisitor that visits all the child tree nodes, and provides
32 * support for maintaining a path for the parent nodes.
33 * To visit nodes of a particular type, just override the
34 * corresponding visitorXYZ method.
35 * Inside your method, call super.visitXYZ to visit descendant
36 * nodes.
37 *
38 * @author Jonathan Gibbons
39 * @since 1.6
40 */
41public class TreePathScanner<R, P> extends TreeScanner<R, P> {
42
43    /**
44     * Scans a tree from a position identified by a TreePath.
45     * @param path the path identifying the node to be scanned
46     * @param p a parameter value passed to visit methods
47     * @return the result value from the visit method
48     */
49    public R scan(TreePath path, P p) {
50        this.path = path;
51        try {
52            return path.getLeaf().accept(this, p);
53        } finally {
54            this.path = null;
55        }
56    }
57
58    /**
59     * Scans a single node.
60     * The current path is updated for the duration of the scan.
61     * @return the result value from the visit method
62     */
63    @Override
64    public R scan(Tree tree, P p) {
65        if (tree == null)
66            return null;
67
68        TreePath prev = path;
69        path = new TreePath(path, tree);
70        try {
71            return tree.accept(this, p);
72        } finally {
73            path = prev;
74        }
75    }
76
77    /**
78     * Returns the current path for the node, as built up by the currently
79     * active set of scan calls.
80     * @return the current path
81     */
82    public TreePath getCurrentPath() {
83        return path;
84    }
85
86    private TreePath path;
87}
88