1 package net.sourceforge.pmd.rules.strings;
2
3 import net.sourceforge.pmd.AbstractRule;
4 import net.sourceforge.pmd.ast.ASTCompilationUnit;
5 import net.sourceforge.pmd.ast.ASTLiteral;
6 import net.sourceforge.pmd.ast.ASTName;
7 import net.sourceforge.pmd.ast.SimpleNode;
8 import net.sourceforge.pmd.symboltable.NameDeclaration;
9 import net.sourceforge.pmd.symboltable.VariableNameDeclaration;
10
11 import java.util.HashSet;
12 import java.util.List;
13 import java.util.Set;
14
15
16 /***
17 * This rule finds places where StringBuffer.toString() is called just to see if
18 * the string is 0 length by either using .equals("") or toString().size()
19 * <p/>
20 * <pre>
21 * StringBuffer sb = new StringBuffer("some string");
22 * if (sb.toString().equals("")) {
23 * // this is wrong
24 * }
25 * if (sb.length() == 0) {
26 * // this is right
27 * }
28 * </pre>
29 *
30 * @author acaplan
31 */
32 public class UseStringBufferLength extends AbstractRule {
33
34
35
36
37
38
39
40
41
42
43
44 private Set alreadySeen = new HashSet();
45
46 public Object visit(ASTCompilationUnit acu, Object data) {
47 alreadySeen.clear();
48 return super.visit(acu, data);
49 }
50
51 public Object visit(ASTName decl, Object data) {
52 if (!decl.getImage().endsWith("toString")) {
53 return data;
54 }
55 NameDeclaration nd = decl.getNameDeclaration();
56 if (!(nd instanceof VariableNameDeclaration)) {
57 return data;
58 }
59 VariableNameDeclaration vnd = (VariableNameDeclaration) nd;
60 if (!vnd.getTypeImage().equals("StringBuffer") || alreadySeen.contains(vnd)) {
61 return data;
62 }
63 alreadySeen.add(vnd);
64
65 SimpleNode parent = (SimpleNode) decl.jjtGetParent().jjtGetParent();
66 for (int jx = 0; jx < parent.jjtGetNumChildren(); jx++) {
67 SimpleNode achild = (SimpleNode) parent.jjtGetChild(jx);
68 if (isViolation(parent, achild)) {
69 addViolation(data, decl);
70 }
71 }
72
73 return data;
74 }
75
76 /***
77 * Check the given node if it calls either .equals or .size we need to check the target
78 */
79 private boolean isViolation(SimpleNode parent, SimpleNode achild) {
80 if ("equals".equals(achild.getImage())) {
81 List literals = parent.findChildrenOfType(ASTLiteral.class);
82 return (!literals.isEmpty() && "\"\"".equals(((SimpleNode) literals.get(0)).getImage()));
83 } else if ("length".equals(achild.getImage())) {
84 return true;
85 }
86 return false;
87 }
88
89
90 }