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


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 package com.puppycrawl.tools.checkstyle.checks.coding;
20
21 import com.puppycrawl.tools.checkstyle.api.Check;
22 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
23 import com.puppycrawl.tools.checkstyle.api.DetailAST;
24 import antlr.collections.AST;
25
26 /**
27  * <p>Checks that string literals are not used with
28  * <code>==</code> or <code>&#33;=</code>.
29  * </p>
30  * <p>
31  * Rationale: Novice Java programmers often use code like
32  * <code>if (x == &quot;something&quot;)</code> when they mean
33  * <code>if (&quot;something&quot;.equals(x))</code>.
34  * </p>
35  *
36  * @author Lars K&uuml;hne
37  */
38 public class StringLiteralEqualityCheck extends Check
39 {
40     /** {@inheritDoc} */
41     public int[] getDefaultTokens()
42     {
43         return new int[] {TokenTypes.EQUAL, TokenTypes.NOT_EQUAL};
44     }
45
46     /** {@inheritDoc} */
47     public void visitToken(DetailAST aAST)
48     {
49         // no need to check for nulls here, == and != always have two children
50 final AST firstChild = aAST.getFirstChild();
51         final AST secondChild = firstChild.getNextSibling();
52
53         if ((firstChild.getType() == TokenTypes.STRING_LITERAL)
54                 || (secondChild.getType() == TokenTypes.STRING_LITERAL))
55         {
56             log(aAST.getLineNo(), aAST.getColumnNo(),
57                     "string.literal.equality", aAST.getText());
58         }
59     }
60 }
61
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