001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2019 the original author or authors.
004//
005// This library is free software; you can redistribute it and/or
006// modify it under the terms of the GNU Lesser General Public
007// License as published by the Free Software Foundation; either
008// version 2.1 of the License, or (at your option) any later version.
009//
010// This library is distributed in the hope that it will be useful,
011// but WITHOUT ANY WARRANTY; without even the implied warranty of
012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
013// Lesser General Public License for more details.
014//
015// You should have received a copy of the GNU Lesser General Public
016// License along with this library; if not, write to the Free Software
017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
018////////////////////////////////////////////////////////////////////////////////
019
020package com.puppycrawl.tools.checkstyle.checks.coding;
021
022import com.puppycrawl.tools.checkstyle.StatelessCheck;
023import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
024import com.puppycrawl.tools.checkstyle.api.DetailAST;
025import com.puppycrawl.tools.checkstyle.api.TokenTypes;
026
027/**
028 * <p>
029 * Checks that switch statement has a &quot;default&quot; clause.
030 * </p>
031 * <p>
032 * Rationale: It's usually a good idea to introduce a
033 * default case in every switch statement. Even if
034 * the developer is sure that all currently possible
035 * cases are covered, this should be expressed in the
036 * default branch, e.g. by using an assertion. This way
037 * the code is protected against later changes, e.g.
038 * introduction of new types in an enumeration type.
039 * </p>
040 * <p>
041 * To configure the check:
042 * </p>
043 * <pre>
044 * &lt;module name=&quot;MissingSwitchDefault&quot;/&gt;
045 * </pre>
046 *
047 * @since 3.1
048 */
049@StatelessCheck
050public class MissingSwitchDefaultCheck extends AbstractCheck {
051
052    /**
053     * A key is pointing to the warning message text in "messages.properties"
054     * file.
055     */
056    public static final String MSG_KEY = "missing.switch.default";
057
058    @Override
059    public int[] getDefaultTokens() {
060        return getRequiredTokens();
061    }
062
063    @Override
064    public int[] getAcceptableTokens() {
065        return getRequiredTokens();
066    }
067
068    @Override
069    public int[] getRequiredTokens() {
070        return new int[] {TokenTypes.LITERAL_SWITCH};
071    }
072
073    @Override
074    public void visitToken(DetailAST ast) {
075        final DetailAST firstCaseGroupAst = ast.findFirstToken(TokenTypes.CASE_GROUP);
076
077        if (!containsDefaultSwitch(firstCaseGroupAst)) {
078            log(ast.getLineNo(), MSG_KEY);
079        }
080    }
081
082    /**
083     * Checks if the case group or its sibling contain the 'default' switch.
084     * @param caseGroupAst first case group to check.
085     * @return true if 'default' switch found.
086     */
087    private static boolean containsDefaultSwitch(DetailAST caseGroupAst) {
088        DetailAST nextAst = caseGroupAst;
089        boolean found = false;
090
091        while (nextAst != null) {
092            if (nextAst.findFirstToken(TokenTypes.LITERAL_DEFAULT) != null) {
093                found = true;
094                break;
095            }
096
097            nextAst = nextAst.getNextSibling();
098        }
099
100        return found;
101    }
102
103}