1 /*
   2  * Copyright (c) 2005, 2006, 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 
  26 package com.sun.source.util;
  27 
  28 import com.sun.source.tree.*;
  29 
  30 /**
  31  * A TreeVisitor that visits all the child tree nodes.
  32  * To visit nodes of a particular type, just override the
  33  * corresponding visitXYZ method.
  34  * Inside your method, call super.visitXYZ to visit descendant
  35  * nodes.
  36  *
  37  * <p>The default implementation of the visitXYZ methods will determine
  38  * a result as follows:
  39  * <ul>
  40  * <li>If the node being visited has no children, the result will be null.
  41  * <li>If the node being visited has one child, the result will be the
  42  * result of calling {@code scan} on that child. The child may be a simple node
  43  * or itself a list of nodes.
  44  * <li> If the node being visited has more than one child, the result will
  45  * be determined by calling {@code scan} each child in turn, and then combining the
  46  * result of each scan after the first with the cumulative result
  47  * so far, as determined by the {@link #reduce} method. Each child may be either
  48  * a simple node of a list of nodes. The default behavior of the {@code reduce}
  49  * method is such that the result of the visitXYZ method will be the result of
  50  * the last child scanned.
  51  * </ul>
  52  *
  53  * <p>Here is an example to count the number of identifier nodes in a tree:
  54  * <pre>
  55  *   class CountIdentifiers extends TreeScanner<Integer,Void> {
  56  *      {@literal @}Override
  57  *      public Integer visitIdentifier(IdentifierTree node, Void p) {
  58  *          return 1;
  59  *      }
  60  *      {@literal @}Override
  61  *      public Integer reduce(Integer r1, Integer r2) {
  62  *          return (r1 == null ? 0 : r1) + (r2 == null ? 0 : r2);
  63  *      }
  64  *   }
  65  * </pre>
  66  *
  67  * @author Peter von der Ah&eacute;
  68  * @author Jonathan Gibbons
  69  * @since 1.6
  70  */
  71 public class TreeScanner<R,P> implements TreeVisitor<R,P> {
  72 
  73     /** Scan a single node.
  74      */
  75     public R scan(Tree node, P p) {
  76         return (node == null) ? null : node.accept(this, p);
  77     }
  78 
  79     private R scanAndReduce(Tree node, P p, R r) {
  80         return reduce(scan(node, p), r);
  81     }
  82 
  83     /** Scan a list of nodes.
  84      */
  85     public R scan(Iterable<? extends Tree> nodes, P p) {
  86         R r = null;
  87         if (nodes != null) {
  88             boolean first = true;
  89             for (Tree node : nodes) {
  90                 r = (first ? scan(node, p) : scanAndReduce(node, p, r));
  91                 first = false;
  92             }
  93         }
  94         return r;
  95     }
  96 
  97     private R scanAndReduce(Iterable<? extends Tree> nodes, P p, R r) {
  98         return reduce(scan(nodes, p), r);
  99     }
 100 
 101     /**
 102      * Reduces two results into a combined result.
 103      * The default implementation is to return the first parameter.
 104      * The general contract of the method is that it may take any action whatsoever.
 105      */
 106     public R reduce(R r1, R r2) {
 107         return r1;
 108     }
 109 
 110 
 111 /* ***************************************************************************
 112  * Visitor methods
 113  ****************************************************************************/
 114 
 115     public R visitCompilationUnit(CompilationUnitTree node, P p) {
 116         R r = scan(node.getPackageAnnotations(), p);
 117         r = scanAndReduce(node.getPackageName(), p, r);
 118         r = scanAndReduce(node.getImports(), p, r);
 119         r = scanAndReduce(node.getTypeDecls(), p, r);
 120         return r;
 121     }
 122 
 123     public R visitImport(ImportTree node, P p) {
 124         return scan(node.getQualifiedIdentifier(), p);
 125     }
 126 
 127     public R visitClass(ClassTree node, P p) {
 128         R r = scan(node.getModifiers(), p);
 129         r = scanAndReduce(node.getTypeParameters(), p, r);
 130         r = scanAndReduce(node.getExtendsClause(), p, r);
 131         r = scanAndReduce(node.getImplementsClause(), p, r);
 132         r = scanAndReduce(node.getMembers(), p, r);
 133         return r;
 134     }
 135 
 136     public R visitMethod(MethodTree node, P p) {
 137         R r = scan(node.getModifiers(), p);
 138         r = scanAndReduce(node.getReturnType(), p, r);
 139         r = scanAndReduce(node.getTypeParameters(), p, r);
 140         r = scanAndReduce(node.getParameters(), p, r);
 141         r = scanAndReduce(node.getReceiverAnnotations(), p, r);
 142         r = scanAndReduce(node.getThrows(), p, r);
 143         r = scanAndReduce(node.getBody(), p, r);
 144         return r;
 145     }
 146 
 147     public R visitVariable(VariableTree node, P p) {
 148         R r = scan(node.getModifiers(), p);
 149         r = scanAndReduce(node.getType(), p, r);
 150         r = scanAndReduce(node.getInitializer(), p, r);
 151         return r;
 152     }
 153 
 154     public R visitEmptyStatement(EmptyStatementTree node, P p) {
 155         return null;
 156     }
 157 
 158     public R visitBlock(BlockTree node, P p) {
 159         return scan(node.getStatements(), p);
 160     }
 161 
 162     public R visitDoWhileLoop(DoWhileLoopTree node, P p) {
 163         R r = scan(node.getStatement(), p);
 164         r = scanAndReduce(node.getCondition(), p, r);
 165         return r;
 166     }
 167 
 168     public R visitWhileLoop(WhileLoopTree node, P p) {
 169         R r = scan(node.getCondition(), p);
 170         r = scanAndReduce(node.getStatement(), p, r);
 171         return r;
 172     }
 173 
 174     public R visitForLoop(ForLoopTree node, P p) {
 175         R r = scan(node.getInitializer(), p);
 176         r = scanAndReduce(node.getCondition(), p, r);
 177         r = scanAndReduce(node.getUpdate(), p, r);
 178         r = scanAndReduce(node.getStatement(), p, r);
 179         return r;
 180     }
 181 
 182     public R visitEnhancedForLoop(EnhancedForLoopTree node, P p) {
 183         R r = scan(node.getVariable(), p);
 184         r = scanAndReduce(node.getExpression(), p, r);
 185         r = scanAndReduce(node.getStatement(), p, r);
 186         return r;
 187     }
 188 
 189     public R visitLabeledStatement(LabeledStatementTree node, P p) {
 190         return scan(node.getStatement(), p);
 191     }
 192 
 193     public R visitSwitch(SwitchTree node, P p) {
 194         R r = scan(node.getExpression(), p);
 195         r = scanAndReduce(node.getCases(), p, r);
 196         return r;
 197     }
 198 
 199     public R visitCase(CaseTree node, P p) {
 200         R r = scan(node.getExpression(), p);
 201         r = scanAndReduce(node.getStatements(), p, r);
 202         return r;
 203     }
 204 
 205     public R visitSynchronized(SynchronizedTree node, P p) {
 206         R r = scan(node.getExpression(), p);
 207         r = scanAndReduce(node.getBlock(), p, r);
 208         return r;
 209     }
 210 
 211     public R visitTry(TryTree node, P p) {
 212         R r = scan(node.getBlock(), p);
 213         r = scanAndReduce(node.getCatches(), p, r);
 214         r = scanAndReduce(node.getFinallyBlock(), p, r);
 215         return r;
 216     }
 217 
 218     public R visitCatch(CatchTree node, P p) {
 219         R r = scan(node.getParameter(), p);
 220         r = scanAndReduce(node.getBlock(), p, r);
 221         return r;
 222     }
 223 
 224     public R visitConditionalExpression(ConditionalExpressionTree node, P p) {
 225         R r = scan(node.getCondition(), p);
 226         r = scanAndReduce(node.getTrueExpression(), p, r);
 227         r = scanAndReduce(node.getFalseExpression(), p, r);
 228         return r;
 229     }
 230 
 231     public R visitIf(IfTree node, P p) {
 232         R r = scan(node.getCondition(), p);
 233         r = scanAndReduce(node.getThenStatement(), p, r);
 234         r = scanAndReduce(node.getElseStatement(), p, r);
 235         return r;
 236     }
 237 
 238     public R visitExpressionStatement(ExpressionStatementTree node, P p) {
 239         return scan(node.getExpression(), p);
 240     }
 241 
 242     public R visitBreak(BreakTree node, P p) {
 243         return null;
 244     }
 245 
 246     public R visitContinue(ContinueTree node, P p) {
 247         return null;
 248     }
 249 
 250     public R visitReturn(ReturnTree node, P p) {
 251         return scan(node.getExpression(), p);
 252     }
 253 
 254     public R visitThrow(ThrowTree node, P p) {
 255         return scan(node.getExpression(), p);
 256     }
 257 
 258     public R visitAssert(AssertTree node, P p) {
 259         R r = scan(node.getCondition(), p);
 260         r = scanAndReduce(node.getDetail(), p, r);
 261         return r;
 262     }
 263 
 264     public R visitMethodInvocation(MethodInvocationTree node, P p) {
 265         R r = scan(node.getTypeArguments(), p);
 266         r = scanAndReduce(node.getMethodSelect(), p, r);
 267         r = scanAndReduce(node.getArguments(), p, r);
 268         return r;
 269     }
 270 
 271     public R visitNewClass(NewClassTree node, P p) {
 272         R r = scan(node.getEnclosingExpression(), p);
 273         r = scanAndReduce(node.getIdentifier(), p, r);
 274         r = scanAndReduce(node.getTypeArguments(), p, r);
 275         r = scanAndReduce(node.getArguments(), p, r);
 276         r = scanAndReduce(node.getClassBody(), p, r);
 277         return r;
 278     }
 279 
 280     public R visitNewArray(NewArrayTree node, P p) {
 281         R r = scan(node.getType(), p);
 282         r = scanAndReduce(node.getDimensions(), p, r);
 283         r = scanAndReduce(node.getInitializers(), p, r);
 284         return r;
 285     }
 286 
 287     public R visitParenthesized(ParenthesizedTree node, P p) {
 288         return scan(node.getExpression(), p);
 289     }
 290 
 291     public R visitAssignment(AssignmentTree node, P p) {
 292         R r = scan(node.getVariable(), p);
 293         r = scanAndReduce(node.getExpression(), p, r);
 294         return r;
 295     }
 296 
 297     public R visitCompoundAssignment(CompoundAssignmentTree node, P p) {
 298         R r = scan(node.getVariable(), p);
 299         r = scanAndReduce(node.getExpression(), p, r);
 300         return r;
 301     }
 302 
 303     public R visitUnary(UnaryTree node, P p) {
 304         return scan(node.getExpression(), p);
 305     }
 306 
 307     public R visitBinary(BinaryTree node, P p) {
 308         R r = scan(node.getLeftOperand(), p);
 309         r = scanAndReduce(node.getRightOperand(), p, r);
 310         return r;
 311     }
 312 
 313     public R visitTypeCast(TypeCastTree node, P p) {
 314         R r = scan(node.getType(), p);
 315         r = scanAndReduce(node.getExpression(), p, r);
 316         return r;
 317     }
 318 
 319     public R visitInstanceOf(InstanceOfTree node, P p) {
 320         R r = scan(node.getExpression(), p);
 321         r = scanAndReduce(node.getType(), p, r);
 322         return r;
 323     }
 324 
 325     public R visitArrayAccess(ArrayAccessTree node, P p) {
 326         R r = scan(node.getExpression(), p);
 327         r = scanAndReduce(node.getIndex(), p, r);
 328         return r;
 329     }
 330 
 331     public R visitMemberSelect(MemberSelectTree node, P p) {
 332         return scan(node.getExpression(), p);
 333     }
 334 
 335     public R visitIdentifier(IdentifierTree node, P p) {
 336         return null;
 337     }
 338 
 339     public R visitLiteral(LiteralTree node, P p) {
 340         return null;
 341     }
 342 
 343     public R visitPrimitiveType(PrimitiveTypeTree node, P p) {
 344         return null;
 345     }
 346 
 347     public R visitArrayType(ArrayTypeTree node, P p) {
 348         return scan(node.getType(), p);
 349     }
 350 
 351     public R visitParameterizedType(ParameterizedTypeTree node, P p) {
 352         R r = scan(node.getType(), p);
 353         r = scanAndReduce(node.getTypeArguments(), p, r);
 354         return r;
 355     }
 356 
 357     public R visitDisjointType(DisjointTypeTree node, P p) {
 358         return scan(node.getTypeComponents(), p);
 359     }
 360 
 361     public R visitTypeParameter(TypeParameterTree node, P p) {
 362         R r = scan(node.getAnnotations(), p);
 363         r = scanAndReduce(node.getBounds(), p, r);
 364         return r;
 365     }
 366 
 367     public R visitWildcard(WildcardTree node, P p) {
 368         return scan(node.getBound(), p);
 369     }
 370 
 371     public R visitModifiers(ModifiersTree node, P p) {
 372         return scan(node.getAnnotations(), p);
 373     }
 374 
 375     public R visitAnnotation(AnnotationTree node, P p) {
 376         R r = scan(node.getAnnotationType(), p);
 377         r = scanAndReduce(node.getArguments(), p, r);
 378         return r;
 379     }
 380 
 381    public R visitAnnotatedType(AnnotatedTypeTree node, P p) {
 382        R r = scan(node.getAnnotations(), p);
 383        r = scanAndReduce(node.getUnderlyingType(), p, r);
 384        return r;
 385    }
 386 
 387     public R visitOther(Tree node, P p) {
 388         return null;
 389     }
 390 
 391     public R visitErroneous(ErroneousTree node, P p) {
 392         return null;
 393     }
 394 }