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1   ////////////////////////////////////////////////////////////////////////////////
2   // checkstyle: Checks Java source code for adherence to a set of rules.
3   // Copyright (C) 2001-2017 the original author or authors.
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 com.puppycrawl.tools.checkstyle.StatelessCheck;
23  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
24  import com.puppycrawl.tools.checkstyle.api.DetailAST;
25  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
26  
27  /**
28   * <p>
29   * Checks for overly complicated boolean expressions. Currently finds code like
30   * {@code if (b == true)}, {@code b || true}, {@code !false},
31   * etc.
32   * </p>
33   * <p>
34   * Rationale: Complex boolean logic makes code hard to understand and maintain.
35   * </p>
36   * <p>
37   * An example of how to configure the check is:
38   * </p>
39   * <pre>
40   * &lt;module name="SimplifyBooleanExpression"/&gt;
41   * </pre>
42   * @author lkuehne
43   */
44  @StatelessCheck
45  public class SimplifyBooleanExpressionCheck
46          extends AbstractCheck {
47  
48      /**
49       * A key is pointing to the warning message text in "messages.properties"
50       * file.
51       */
52      public static final String MSG_KEY = "simplify.expression";
53  
54      @Override
55      public int[] getDefaultTokens() {
56          return getRequiredTokens();
57      }
58  
59      @Override
60      public int[] getAcceptableTokens() {
61          return getRequiredTokens();
62      }
63  
64      @Override
65      public int[] getRequiredTokens() {
66          return new int[] {TokenTypes.LITERAL_TRUE, TokenTypes.LITERAL_FALSE};
67      }
68  
69      @Override
70      public void visitToken(DetailAST ast) {
71          final DetailAST parent = ast.getParent();
72          switch (parent.getType()) {
73              case TokenTypes.NOT_EQUAL:
74              case TokenTypes.EQUAL:
75              case TokenTypes.LNOT:
76              case TokenTypes.LOR:
77              case TokenTypes.LAND:
78                  log(parent.getLineNo(), parent.getColumnNo(),
79                      MSG_KEY);
80                  break;
81              default:
82                  break;
83          }
84      }
85  }