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


1 package net.sourceforge.pmd.rules;
2
3 import net.sourceforge.pmd.AbstractRule;
4 import net.sourceforge.pmd.ast.ASTEqualityExpression;
5 import net.sourceforge.pmd.ast.ASTLiteral;
6 import net.sourceforge.pmd.ast.ASTPrimitiveType;
7 import net.sourceforge.pmd.ast.ASTRelationalExpression;
8 import net.sourceforge.pmd.ast.ASTVariableDeclaratorId;
9 import net.sourceforge.pmd.ast.SimpleNode;
10 import net.sourceforge.pmd.symboltable.NameOccurrence;
11
12 import java.util.Iterator JavaDoc;
13 import java.util.List JavaDoc;
14
15 /**
16  * This is an abstract rule for patterns which compare a method invocation to 0.
17  * It could be further abstracted to find code that compares something to
18  * another definable pattern
19  *
20  * @author acaplan
21  */
22 public abstract class AbstractInefficientZeroCheck extends AbstractRule {
23
24     public abstract boolean appliesToClassName(String JavaDoc name);
25
26     public abstract boolean isTargetMethod(NameOccurrence occ);
27
28     public Object JavaDoc visit(ASTVariableDeclaratorId node, Object JavaDoc data) {
29         SimpleNode nameNode = node.getTypeNameNode();
30         if (nameNode instanceof ASTPrimitiveType) {
31             return data;
32         }
33         if (!appliesToClassName(node.getNameDeclaration().getTypeImage())) {
34             return data;
35         }
36
37         List JavaDoc declars = node.getUsages();
38         for (Iterator JavaDoc i = declars.iterator(); i.hasNext();) {
39             NameOccurrence occ = (NameOccurrence) i.next();
40             if (!isTargetMethod(occ)) {
41                 continue;
42             }
43             SimpleNode expr = (SimpleNode) occ.getLocation().jjtGetParent().jjtGetParent().jjtGetParent();
44             if ((expr instanceof ASTEqualityExpression ||
45                     (expr instanceof ASTRelationalExpression && ">".equals(expr.getImage())))
46                 && isCompareZero(expr)) {
47                 addViolation(data, occ.getLocation());
48             }
49         }
50         return data;
51     }
52
53     /**
54      * We only need to report if this is comparing against 0
55      *
56      * @param equality
57      * @return true if this is comparing to 0 else false
58      */
59     private boolean isCompareZero(SimpleNode equality) {
60         return (checkComparison(equality, 0) || checkComparison(equality, 1));
61
62     }
63
64     /**
65      * Checks if the equality expression passed in is of comparing against the
66      * value passed in as i
67      *
68      * @param equality
69      * @param i
70      * The ordinal in the equality expression to check
71      * @return true if the value in position i is 0, else false
72      */
73     private boolean checkComparison(SimpleNode equality, int i) {
74         SimpleNode target = (SimpleNode) equality.jjtGetChild(i).jjtGetChild(0);
75         if (target.jjtGetNumChildren() == 0) {
76             return false;
77         }
78         target = (SimpleNode) target.jjtGetChild(0);
79         return (target instanceof ASTLiteral && "0".equals(target.getImage()));
80     }
81
82 }
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