001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2017 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 &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 * An example of how to configure the check is:
042 * </p>
043 * <pre>
044 * &lt;module name="MissingSwitchDefault"/&gt;
045 * </pre>
046 * @author o_sukhodolsky
047 */
048@StatelessCheck
049public class MissingSwitchDefaultCheck extends AbstractCheck {
050
051    /**
052     * A key is pointing to the warning message text in "messages.properties"
053     * file.
054     */
055    public static final String MSG_KEY = "missing.switch.default";
056
057    @Override
058    public int[] getDefaultTokens() {
059        return getRequiredTokens();
060    }
061
062    @Override
063    public int[] getAcceptableTokens() {
064        return getRequiredTokens();
065    }
066
067    @Override
068    public int[] getRequiredTokens() {
069        return new int[] {TokenTypes.LITERAL_SWITCH};
070    }
071
072    @Override
073    public void visitToken(DetailAST ast) {
074        final DetailAST firstCaseGroupAst = ast.findFirstToken(TokenTypes.CASE_GROUP);
075
076        if (!containsDefaultSwitch(firstCaseGroupAst)) {
077            log(ast.getLineNo(), MSG_KEY);
078        }
079    }
080
081    /**
082     * Checks if the case group or its sibling contain the 'default' switch.
083     * @param caseGroupAst first case group to check.
084     * @return true if 'default' switch found.
085     */
086    private static boolean containsDefaultSwitch(DetailAST caseGroupAst) {
087        DetailAST nextAst = caseGroupAst;
088        boolean found = false;
089
090        while (nextAst != null) {
091            if (nextAst.findFirstToken(TokenTypes.LITERAL_DEFAULT) != null) {
092                found = true;
093                break;
094            }
095
096            nextAst = nextAst.getNextSibling();
097        }
098
099        return found;
100    }
101}