51 * the last child scanned.
52 * </ul>
53 *
54 * <p>Here is an example to count the number of erroneous nodes in a tree:
55 * <pre>
56 * class CountErrors extends DocTreeScanner<Integer,Void> {
57 * {@literal @}Override
58 * public Integer visitErroneous(ErroneousTree node, Void p) {
59 * return 1;
60 * }
61 * {@literal @}Override
62 * public Integer reduce(Integer r1, Integer r2) {
63 * return (r1 == null ? 0 : r1) + (r2 == null ? 0 : r2);
64 * }
65 * }
66 * </pre>
67 *
68 * @since 1.8
69 */
70 public class DocTreeScanner<R,P> implements DocTreeVisitor<R,P> {
71
72 /**
73 * Scans a single node.
74 * @param node the node to be scanned
75 * @param p a parameter value passed to the visit method
76 * @return the result value from the visit method
77 */
78 public R scan(DocTree node, P p) {
79 return (node == null) ? null : node.accept(this, p);
80 }
81
82 private R scanAndReduce(DocTree node, P p, R r) {
83 return reduce(scan(node, p), r);
84 }
85
86 /**
87 * Scans a sequence of nodes.
88 * @param nodes the nodes to be scanned
89 * @param p a parameter value to be passed to the visit method for each node
90 * @return the combined return value from the visit methods.
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51 * the last child scanned.
52 * </ul>
53 *
54 * <p>Here is an example to count the number of erroneous nodes in a tree:
55 * <pre>
56 * class CountErrors extends DocTreeScanner<Integer,Void> {
57 * {@literal @}Override
58 * public Integer visitErroneous(ErroneousTree node, Void p) {
59 * return 1;
60 * }
61 * {@literal @}Override
62 * public Integer reduce(Integer r1, Integer r2) {
63 * return (r1 == null ? 0 : r1) + (r2 == null ? 0 : r2);
64 * }
65 * }
66 * </pre>
67 *
68 * @since 1.8
69 */
70 public class DocTreeScanner<R,P> implements DocTreeVisitor<R,P> {
71 /**
72 * Constructs a {@code DocTreeScanner}.
73 */
74 public DocTreeScanner() {}
75
76 /**
77 * Scans a single node.
78 * @param node the node to be scanned
79 * @param p a parameter value passed to the visit method
80 * @return the result value from the visit method
81 */
82 public R scan(DocTree node, P p) {
83 return (node == null) ? null : node.accept(this, p);
84 }
85
86 private R scanAndReduce(DocTree node, P p, R r) {
87 return reduce(scan(node, p), r);
88 }
89
90 /**
91 * Scans a sequence of nodes.
92 * @param nodes the nodes to be scanned
93 * @param p a parameter value to be passed to the visit method for each node
94 * @return the combined return value from the visit methods.
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