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1   ////////////////////////////////////////////////////////////////////////////////
2   // checkstyle: Checks Java source code for adherence to a set of rules.
3   // Copyright (C) 2001-2018 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 that switch statement has &quot;default&quot; clause.
30   * </p>
31   * <p>
32   * Rationale: It's usually a good idea to introduce a
33   * default case in every switch statement. Even if
34   * the developer is sure that all currently possible
35   * cases are covered, this should be expressed in the
36   * default branch, e.g. by using an assertion. This way
37   * the code is protected against later changes, e.g.
38   * introduction of new types in an enumeration type.
39   * </p>
40   * <p>
41   * An example of how to configure the check is:
42   * </p>
43   * <pre>
44   * &lt;module name="MissingSwitchDefault"/&gt;
45   * </pre>
46   * @author o_sukhodolsky
47   */
48  @StatelessCheck
49  public class MissingSwitchDefaultCheck extends AbstractCheck {
50  
51      /**
52       * A key is pointing to the warning message text in "messages.properties"
53       * file.
54       */
55      public static final String MSG_KEY = "missing.switch.default";
56  
57      @Override
58      public int[] getDefaultTokens() {
59          return getRequiredTokens();
60      }
61  
62      @Override
63      public int[] getAcceptableTokens() {
64          return getRequiredTokens();
65      }
66  
67      @Override
68      public int[] getRequiredTokens() {
69          return new int[] {TokenTypes.LITERAL_SWITCH};
70      }
71  
72      @Override
73      public void visitToken(DetailAST ast) {
74          final DetailAST firstCaseGroupAst = ast.findFirstToken(TokenTypes.CASE_GROUP);
75  
76          if (!containsDefaultSwitch(firstCaseGroupAst)) {
77              log(ast.getLineNo(), MSG_KEY);
78          }
79      }
80  
81      /**
82       * Checks if the case group or its sibling contain the 'default' switch.
83       * @param caseGroupAst first case group to check.
84       * @return true if 'default' switch found.
85       */
86      private static boolean containsDefaultSwitch(DetailAST caseGroupAst) {
87          DetailAST nextAst = caseGroupAst;
88          boolean found = false;
89  
90          while (nextAst != null) {
91              if (nextAst.findFirstToken(TokenTypes.LITERAL_DEFAULT) != null) {
92                  found = true;
93                  break;
94              }
95  
96              nextAst = nextAst.getNextSibling();
97          }
98  
99          return found;
100     }
101 
102 }