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/*
* Copyright (c) 2005, 2016, 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
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*/
package org.openjdk.source.util;
import org.openjdk.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.
*
* The default implementation of the visitXYZ methods will determine
* a result as follows:
*
* - If the node being visited has no children, the result will be {@code null}.
*
- 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.
*
- 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.
*
*
* Here is an example to count the number of identifier nodes in a tree:
*
* class CountIdentifiers extends TreeScanner<Integer,Void> {
* {@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);
* }
* }
*
*
* @param the return type of this visitor's methods. Use {@link
* Void} for visitors that do not need to return results.
* @param the type of the additional parameter to this visitor's
* methods. Use {@code Void} for visitors that do not need an
* additional parameter.
*
* @author Peter von der Ahé
* @author Jonathan Gibbons
* @since 1.6
*/
public class TreeScanner implements TreeVisitor {
/**
* Scans a single node.
* @param tree the node to be scanned
* @param p a parameter value passed to the visit method
* @return the result value from the visit method
*/
public R scan(Tree tree, P p) {
return (tree == null) ? null : tree.accept(this, p);
}
private R scanAndReduce(Tree node, P p, R r) {
return reduce(scan(node, p), r);
}
/**
* Scans a sequence of nodes.
* @param nodes the nodes to be scanned
* @param p a parameter value to be passed to the visit method for each node
* @return the combined return value from the visit methods.
* The values are combined using the {@link #reduce reduce} method.
*/
public R scan(Iterable 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 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.
* @param r1 the first of the values to be combined
* @param r2 the second of the values to be combined
* @return the result of combining the two parameters
*/
public R reduce(R r1, R r2) {
return r1;
}
/* ***************************************************************************
* Visitor methods
****************************************************************************/
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitCompilationUnit(CompilationUnitTree node, P p) {
R r = scan(node.getPackage(), p);
r = scanAndReduce(node.getImports(), p, r);
r = scanAndReduce(node.getTypeDecls(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitPackage(PackageTree node, P p) {
R r = scan(node.getAnnotations(), p);
r = scanAndReduce(node.getPackageName(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitImport(ImportTree node, P p) {
return scan(node.getQualifiedIdentifier(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
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;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
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;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
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;
}
/**
* {@inheritDoc} This implementation returns {@code null}.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitEmptyStatement(EmptyStatementTree node, P p) {
return null;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitBlock(BlockTree node, P p) {
return scan(node.getStatements(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitDoWhileLoop(DoWhileLoopTree node, P p) {
R r = scan(node.getStatement(), p);
r = scanAndReduce(node.getCondition(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitWhileLoop(WhileLoopTree node, P p) {
R r = scan(node.getCondition(), p);
r = scanAndReduce(node.getStatement(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
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;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
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;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitLabeledStatement(LabeledStatementTree node, P p) {
return scan(node.getStatement(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitSwitch(SwitchTree node, P p) {
R r = scan(node.getExpression(), p);
r = scanAndReduce(node.getCases(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitCase(CaseTree node, P p) {
R r = scan(node.getExpression(), p);
r = scanAndReduce(node.getStatements(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitSynchronized(SynchronizedTree node, P p) {
R r = scan(node.getExpression(), p);
r = scanAndReduce(node.getBlock(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
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;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitCatch(CatchTree node, P p) {
R r = scan(node.getParameter(), p);
r = scanAndReduce(node.getBlock(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
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;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
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;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitExpressionStatement(ExpressionStatementTree node, P p) {
return scan(node.getExpression(), p);
}
/**
* {@inheritDoc} This implementation returns {@code null}.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitBreak(BreakTree node, P p) {
return null;
}
/**
* {@inheritDoc} This implementation returns {@code null}.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitContinue(ContinueTree node, P p) {
return null;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitReturn(ReturnTree node, P p) {
return scan(node.getExpression(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitThrow(ThrowTree node, P p) {
return scan(node.getExpression(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitAssert(AssertTree node, P p) {
R r = scan(node.getCondition(), p);
r = scanAndReduce(node.getDetail(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
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;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
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;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
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;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitLambdaExpression(LambdaExpressionTree node, P p) {
R r = scan(node.getParameters(), p);
r = scanAndReduce(node.getBody(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitParenthesized(ParenthesizedTree node, P p) {
return scan(node.getExpression(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitAssignment(AssignmentTree node, P p) {
R r = scan(node.getVariable(), p);
r = scanAndReduce(node.getExpression(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitCompoundAssignment(CompoundAssignmentTree node, P p) {
R r = scan(node.getVariable(), p);
r = scanAndReduce(node.getExpression(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitUnary(UnaryTree node, P p) {
return scan(node.getExpression(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitBinary(BinaryTree node, P p) {
R r = scan(node.getLeftOperand(), p);
r = scanAndReduce(node.getRightOperand(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitTypeCast(TypeCastTree node, P p) {
R r = scan(node.getType(), p);
r = scanAndReduce(node.getExpression(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitInstanceOf(InstanceOfTree node, P p) {
R r = scan(node.getExpression(), p);
r = scanAndReduce(node.getType(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitArrayAccess(ArrayAccessTree node, P p) {
R r = scan(node.getExpression(), p);
r = scanAndReduce(node.getIndex(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitMemberSelect(MemberSelectTree node, P p) {
return scan(node.getExpression(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitMemberReference(MemberReferenceTree node, P p) {
R r = scan(node.getQualifierExpression(), p);
r = scanAndReduce(node.getTypeArguments(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation returns {@code null}.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitIdentifier(IdentifierTree node, P p) {
return null;
}
/**
* {@inheritDoc} This implementation returns {@code null}.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitLiteral(LiteralTree node, P p) {
return null;
}
/**
* {@inheritDoc} This implementation returns {@code null}.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitPrimitiveType(PrimitiveTypeTree node, P p) {
return null;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitArrayType(ArrayTypeTree node, P p) {
return scan(node.getType(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitParameterizedType(ParameterizedTypeTree node, P p) {
R r = scan(node.getType(), p);
r = scanAndReduce(node.getTypeArguments(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitUnionType(UnionTypeTree node, P p) {
return scan(node.getTypeAlternatives(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitIntersectionType(IntersectionTypeTree node, P p) {
return scan(node.getBounds(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitTypeParameter(TypeParameterTree node, P p) {
R r = scan(node.getAnnotations(), p);
r = scanAndReduce(node.getBounds(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitWildcard(WildcardTree node, P p) {
return scan(node.getBound(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitModifiers(ModifiersTree node, P p) {
return scan(node.getAnnotations(), p);
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitAnnotation(AnnotationTree node, P p) {
R r = scan(node.getAnnotationType(), p);
r = scanAndReduce(node.getArguments(), p, r);
return r;
}
/**
* {@inheritDoc} This implementation scans the children in left to right order.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitAnnotatedType(AnnotatedTypeTree node, P p) {
R r = scan(node.getAnnotations(), p);
r = scanAndReduce(node.getUnderlyingType(), p, r);
return r;
}
@Override
public R visitModule(ModuleTree node, P p) {
R r = scan(node.getAnnotations(), p);
r = scanAndReduce(node.getName(), p, r);
r = scanAndReduce(node.getDirectives(), p, r);
return r;
}
@Override
public R visitExports(ExportsTree node, P p) {
R r = scan(node.getPackageName(), p);
r = scanAndReduce(node.getModuleNames(), p, r);
return r;
}
@Override
public R visitOpens(OpensTree node, P p) {
R r = scan(node.getPackageName(), p);
r = scanAndReduce(node.getModuleNames(), p, r);
return r;
}
@Override
public R visitProvides(ProvidesTree node, P p) {
R r = scan(node.getServiceName(), p);
r = scanAndReduce(node.getImplementationNames(), p, r);
return r;
}
@Override
public R visitRequires(RequiresTree node, P p) {
return scan(node.getModuleName(), p);
}
@Override
public R visitUses(UsesTree node, P p) {
return scan(node.getServiceName(), p);
}
/**
* {@inheritDoc} This implementation returns {@code null}.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitOther(Tree node, P p) {
return null;
}
/**
* {@inheritDoc} This implementation returns {@code null}.
*
* @param node {@inheritDoc}
* @param p {@inheritDoc}
* @return the result of scanning
*/
@Override
public R visitErroneous(ErroneousTree node, P p) {
return null;
}
}