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Java > Open Source Codes > com > puppycrawl > tools > checkstyle > checks > coding > SimplifyBooleanReturnCheck


1 ////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code for adherence to a set of rules.
3 // Copyright (C) 2001-2005 Oliver Burn
4 //
5 // This library is free software; you can redistribute it and/or
6 // modify it under the terms of the GNU Lesser General Public
7 // License as published by the Free Software Foundation; either
8 // version 2.1 of the License, or (at your option) any later version.
9 //
10 // This library is distributed in the hope that it will be useful,
11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 // Lesser General Public License for more details.
14 //
15 // You should have received a copy of the GNU Lesser General Public
16 // License along with this library; if not, write to the Free Software
17 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 ////////////////////////////////////////////////////////////////////////////////
19
20 package com.puppycrawl.tools.checkstyle.checks.coding;
21
22 import antlr.collections.AST;
23 import com.puppycrawl.tools.checkstyle.api.Check;
24 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
25 import com.puppycrawl.tools.checkstyle.api.DetailAST;
26
27
28 /**
29  * <p>
30  * Checks for overly complicated boolean return statements.
31  * Idea shamelessly stolen from the equivalent PMD rule (pmd.sourceforge.net).
32  * </p>
33  * <p>
34  * An example of how to configure the check is:
35  * </p>
36  * <pre>
37  * &lt;module name="SimplifyBooleanReturn"/&gt;
38  * </pre>
39  * @author Lars Kühne
40  */
41 public class SimplifyBooleanReturnCheck
42     extends Check
43 {
44     /** {@inheritDoc} */
45     public int[] getDefaultTokens()
46     {
47         return new int[] {TokenTypes.LITERAL_IF};
48     }
49
50     /** {@inheritDoc} */
51     public void visitToken(DetailAST aAST)
52     {
53         // LITERAL_IF has the following four or five children:
54 // '('
55 // condition
56 // ')'
57 // thenStatement
58 // [ LITERAL_ELSE (with the elseStatement as a child) ]
59
60         // don't bother if this is not if then else
61 final AST elseLiteral =
62             aAST.findFirstToken(TokenTypes.LITERAL_ELSE);
63         if (elseLiteral == null) {
64             return;
65         }
66         final AST elseStatement = elseLiteral.getFirstChild();
67
68         // skip '(' and ')'
69 // TODO: Introduce helpers in DetailAST
70 final AST condition = aAST.getFirstChild().getNextSibling();
71         final AST thenStatement = condition.getNextSibling().getNextSibling();
72
73         if (returnsOnlyBooleanLiteral(thenStatement)
74             && returnsOnlyBooleanLiteral(elseStatement))
75         {
76             log(aAST.getLineNo(), aAST.getColumnNo(), "simplify.boolreturn");
77         }
78     }
79
80     /**
81      * Returns if an AST is a return statment with a boolean literal
82      * or a compound statement that contains only such a return statement.
83      *
84      * Returns <code>true</code> iff aAST represents
85      * <br>
86      * <pre>
87      * return true/false;
88      * <pre>
89      * or
90      * <br>
91      * <pre>
92      * {
93      * return true/false;
94      * }
95      * <pre>
96      *
97      * @param aAST the sytax tree to check
98      * @return if aAST is a return statment with a boolean literal.
99      */
100     private static boolean returnsOnlyBooleanLiteral(AST aAST)
101     {
102         if (isBooleanLiteralReturnStatement(aAST)) {
103             return true;
104         }
105
106         final AST firstStmnt = aAST.getFirstChild();
107         return isBooleanLiteralReturnStatement(firstStmnt);
108     }
109
110     /**
111      * Returns if an AST is a return statment with a boolean literal.
112      *
113      * Returns <code>true</code> iff aAST represents
114      * <br>
115      * <pre>
116      * return true/false;
117      * <pre>
118      *
119      * @param aAST the sytax tree to check
120      * @return if aAST is a return statment with a boolean literal.
121      */
122     private static boolean isBooleanLiteralReturnStatement(AST aAST)
123     {
124         if ((aAST == null) || (aAST.getType() != TokenTypes.LITERAL_RETURN)) {
125             return false;
126         }
127
128         final AST expr = aAST.getFirstChild();
129
130         if ((expr == null) || (expr.getType() == TokenTypes.SEMI)) {
131             return false;
132         }
133
134         final AST value = expr.getFirstChild();
135         return isBooleanLiteralType(value.getType());
136     }
137
138     /**
139      * Checks if a token type is a literal true or false.
140      * @param aTokenType the TokenType
141      * @return true iff aTokenType is LITERAL_TRUE or LITERAL_FALSE
142      */
143     private static boolean isBooleanLiteralType(final int aTokenType)
144     {
145         final boolean isTrue = (aTokenType == TokenTypes.LITERAL_TRUE);
146         final boolean isFalse = (aTokenType == TokenTypes.LITERAL_FALSE);
147         return isTrue || isFalse;
148     }
149 }
150
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