01 package net.sourceforge.pmd.lang.java.rule.unnecessary;
02
03 import java.util.HashMap;
04 import java.util.Map;
05 import java.util.Set;
06
07 import net.sourceforge.pmd.lang.ast.Node;
08 import net.sourceforge.pmd.lang.java.ast.ASTLocalVariableDeclaration;
09 import net.sourceforge.pmd.lang.java.ast.ASTStatementExpression;
10 import net.sourceforge.pmd.lang.java.ast.ASTType;
11 import net.sourceforge.pmd.lang.java.ast.ASTVariableDeclaratorId;
12 import net.sourceforge.pmd.lang.java.rule.AbstractJavaRule;
13 import net.sourceforge.pmd.lang.java.symboltable.NameOccurrence;
14 import net.sourceforge.pmd.util.CollectionUtil;
15
16 /**
17 * An operation on an Immutable object (String, BigDecimal or BigInteger) won't change
18 * the object itself. The result of the operation is a new object. Therefore,
19 * ignoring the operation result is an error.
20 */
21 public class UselessOperationOnImmutableRule extends AbstractJavaRule {
22
23 /**
24 * These are the BigDecimal methods which are immutable
25 */
26 private static final Set<String> BIG_DECIMAL_METHODS = CollectionUtil.asSet(new String[] { ".abs", ".add", ".divide", ".divideToIntegralValue", ".max", ".min", ".movePointLeft", ".movePointRight", ".multiply", ".negate", ".plus", ".pow", ".remainder", ".round", ".scaleByPowerOfTen", ".setScale", ".stripTrailingZeros", ".subtract", ".ulp" });
27
28 /**
29 * These are the BigInteger methods which are immutable
30 */
31 private static final Set<String> BIG_INTEGER_METHODS = CollectionUtil.asSet(new String[] { ".abs", ".add", ".and", ".andNot", ".clearBit", ".divide", ".flipBit", ".gcd", ".max", ".min", ".mod", ".modInverse", ".modPow", ".multiply", ".negate", ".nextProbablePrine", ".not", ".or", ".pow", ".remainder", ".setBit", ".shiftLeft", ".shiftRight", ".subtract", ".xor" });
32
33 /**
34 * These are the String methods which are immutable
35 */
36 private static final Set<String> STRING_METHODS = CollectionUtil.asSet(new String[] { ".concat", ".intern", ".replace", ".replaceAll", ".replaceFirst", ".substring", ".toLowerCase", ".toString", ".toUpperCase", ".trim" });
37
38 /**
39 * These are the classes that the rule can apply to
40 */
41 private static final Map<String, Set<String>> MAP_CLASSES = new HashMap<String, Set<String>>();
42 static {
43 MAP_CLASSES.put("java.math.BigDecimal", BIG_DECIMAL_METHODS);
44 MAP_CLASSES.put("BigDecimal", BIG_DECIMAL_METHODS);
45 MAP_CLASSES.put("java.math.BigInteger", BIG_INTEGER_METHODS);
46 MAP_CLASSES.put("BigInteger", BIG_INTEGER_METHODS);
47 MAP_CLASSES.put("java.lang.String", STRING_METHODS);
48 MAP_CLASSES.put("String", STRING_METHODS);
49 }
50
51 @Override
52 public Object visit(ASTLocalVariableDeclaration node, Object data) {
53
54 ASTVariableDeclaratorId var = getDeclaration(node);
55 if (var == null) {
56 return super.visit(node, data);
57 }
58 String variableName = var.getImage();
59 for (NameOccurrence no: var.getUsages()) {
60 // FIXME - getUsages will return everything with the same name as the variable,
61 // see JUnit test, case 6. Changing to Node below, revisit when getUsages is fixed
62 Node sn = no.getLocation();
63 Node primaryExpression = sn.jjtGetParent().jjtGetParent();
64 Class<? extends Node> parentClass = primaryExpression.jjtGetParent().getClass();
65 if (parentClass.equals(ASTStatementExpression.class)) {
66 String methodCall = sn.getImage().substring(variableName.length());
67 ASTType nodeType = node.getTypeNode();
68 if ( nodeType != null ) {
69 if ( MAP_CLASSES.get(nodeType.getTypeImage()).contains(methodCall)) {
70 addViolation(data, sn);
71 }
72 }
73 }
74 }
75 return super.visit(node, data);
76 }
77
78 /**
79 * This method checks the variable declaration if it is on a class we care
80 * about. If it is, it returns the DeclaratorId
81 *
82 * @param node
83 * The ASTLocalVariableDeclaration which is a problem
84 * @return ASTVariableDeclaratorId
85 */
86 private ASTVariableDeclaratorId getDeclaration(ASTLocalVariableDeclaration node) {
87 ASTType type = node.getTypeNode();
88 if (MAP_CLASSES.keySet().contains(type.getTypeImage())) {
89 return node.getFirstDescendantOfType(ASTVariableDeclaratorId.class);
90 }
91 return null;
92 }
93 }
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