001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2016 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.api.Check;
023import com.puppycrawl.tools.checkstyle.api.DetailAST;
024import com.puppycrawl.tools.checkstyle.api.TokenTypes;
025
026/**
027 * <p>
028 * Checks that switch statement has &quot;default&quot; clause.
029 * </p>
030 * <p>
031 * Rationale: It's usually a good idea to introduce a
032 * default case in every switch statement. Even if
033 * the developer is sure that all currently possible
034 * cases are covered, this should be expressed in the
035 * default branch, e.g. by using an assertion. This way
036 * the code is protected against later changes, e.g.
037 * introduction of new types in an enumeration type.
038 * </p>
039 * <p>
040 * An example of how to configure the check is:
041 * </p>
042 * <pre>
043 * &lt;module name="MissingSwitchDefault"/&gt;
044 * </pre>
045 * @author o_sukhodolsky
046 */
047public class MissingSwitchDefaultCheck extends Check {
048
049    /**
050     * A key is pointing to the warning message text in "messages.properties"
051     * file.
052     */
053    public static final String MSG_KEY = "missing.switch.default";
054
055    @Override
056    public int[] getDefaultTokens() {
057        return new int[] {TokenTypes.LITERAL_SWITCH};
058    }
059
060    @Override
061    public int[] getAcceptableTokens() {
062        return getDefaultTokens();
063    }
064
065    @Override
066    public int[] getRequiredTokens() {
067        return getDefaultTokens();
068    }
069
070    @Override
071    public void visitToken(DetailAST ast) {
072        final DetailAST firstCaseGroupAst = ast.findFirstToken(TokenTypes.CASE_GROUP);
073
074        if (!containsDefaultSwitch(firstCaseGroupAst)) {
075            log(ast.getLineNo(), MSG_KEY);
076        }
077    }
078
079    /**
080     * Checks if the case group or its sibling contain the 'default' switch.
081     * @param caseGroupAst first case group to check.
082     * @return true if 'default' switch found.
083     */
084    private static boolean containsDefaultSwitch(DetailAST caseGroupAst) {
085        DetailAST nextAst = caseGroupAst;
086        boolean found = false;
087
088        while (nextAst != null) {
089            if (nextAst.findFirstToken(TokenTypes.LITERAL_DEFAULT) != null) {
090                found = true;
091                break;
092            }
093
094            nextAst = nextAst.getNextSibling();
095        }
096
097        return found;
098    }
099}