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Java > Open Source Codes > net > sourceforge > pmd > rules > UselessOperationOnImmutable


1 package net.sourceforge.pmd.rules;
2
3 import java.util.Iterator JavaDoc;
4 import java.util.Set JavaDoc;
5
6 import net.sourceforge.pmd.AbstractRule;
7 import net.sourceforge.pmd.ast.ASTExpression;
8 import net.sourceforge.pmd.ast.ASTLocalVariableDeclaration;
9 import net.sourceforge.pmd.ast.ASTName;
10 import net.sourceforge.pmd.ast.ASTType;
11 import net.sourceforge.pmd.ast.ASTVariableDeclaratorId;
12 import net.sourceforge.pmd.symboltable.NameOccurrence;
13 import net.sourceforge.pmd.util.CollectionUtil;
14
15 /**
16  * An operation on an Immutable object (BigDecimal or BigInteger) won't change
17  * the object itself. The result of the operation is a new object. Therefore,
18  * ignoring the operation result is an error.
19  */
20 public class UselessOperationOnImmutable extends AbstractRule {
21
22     /**
23      * These are the methods which are immutable
24      */
25     private static final Set JavaDoc targetMethods = CollectionUtil.asSet(new String JavaDoc[] { ".add", ".multiply", ".divide", ".subtract", ".setScale", ".negate", ".movePointLeft", ".movePointRight", ".pow", ".shiftLeft", ".shiftRight" });
26
27     /**
28      * These are the classes that the rule can apply to
29      */
30     private static final Set JavaDoc targetClasses = CollectionUtil.asSet(new String JavaDoc[] { "java.math.BigDecimal", "BigDecimal", "java.math.BigInteger", "BigInteger" });
31
32     public Object JavaDoc visit(ASTLocalVariableDeclaration node, Object JavaDoc data) {
33
34         ASTVariableDeclaratorId var = getDeclaration(node);
35         if (var == null) {
36             return super.visit(node, data);
37         }
38         String JavaDoc variableName = var.getImage();
39         for (Iterator JavaDoc it = var.getUsages().iterator(); it.hasNext();) {
40             NameOccurrence no = (NameOccurrence) it.next();
41             ASTName sn = (ASTName) no.getLocation();
42             if (!sn.jjtGetParent().jjtGetParent().jjtGetParent().getClass().equals(ASTExpression.class)) {
43                 String JavaDoc methodCall = sn.getImage().substring(variableName.length());
44                 if (targetMethods.contains(methodCall)) {
45                     addViolation(data, sn);
46                 }
47             }
48         }
49         return super.visit(node, data);
50     }
51
52     /**
53      * This method checks the variable declaration if it is on a class we care
54      * about. If it is, it returns the DeclaratorId
55      *
56      * @param node
57      * The ASTLocalVariableDeclaration which is a problem
58      * @return ASTVariableDeclaratorId
59      */
60     private ASTVariableDeclaratorId getDeclaration(ASTLocalVariableDeclaration node) {
61         ASTType type = node.getTypeNode();
62         if (targetClasses.contains(type.getTypeImage())) {
63             return (ASTVariableDeclaratorId) node.jjtGetChild(1).jjtGetChild(0);
64         }
65         return null;
66     }
67 }
68
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