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 java.util.Objects;
023
024import com.puppycrawl.tools.checkstyle.StatelessCheck;
025import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
026import com.puppycrawl.tools.checkstyle.api.DetailAST;
027import com.puppycrawl.tools.checkstyle.api.TokenTypes;
028
029/**
030 * <p>
031 * Check that the {@code default} is after all the cases in a {@code switch} statement.
032 * </p>
033 * <p>
034 * Rationale: Java allows {@code default} anywhere within the
035 * {@code switch} statement. But it is more readable if it comes after the last {@code case}.
036 * </p>
037 * <ul>
038 * <li>
039 * Property {@code skipIfLastAndSharedWithCase} - Control whether to allow {@code default}
040 * along with {@code case} if they are not last.
041 * Default value is {@code false}.
042 * </li>
043 * </ul>
044 * <p>
045 * To configure the check:
046 * </p>
047 * <pre>
048 * &lt;module name=&quot;DefaultComesLast&quot;/&gt;
049 * </pre>
050 * <p>
051 * To configure the check for skipIfLastAndSharedWithCase:
052 * </p>
053 * <pre>
054 * &lt;module name=&quot;DefaultComesLast&quot;&gt;
055 *   &lt;property name=&quot;skipIfLastAndSharedWithCase&quot; value=&quot;true&quot;/&gt;
056 * &lt;/module&gt;
057 * </pre>
058 * <p>
059 * Example when skipIfLastAndSharedWithCase is set to true.
060 * </p>
061 * <pre>
062 * switch (i) {
063 *   case 1:
064 *     break;
065 *   case 2:
066 *   default: // No violation with the new option is expected
067 *     break;
068 *   case 3:
069 *     break;
070 * }
071 * switch (i) {
072 *   case 1:
073 *     break;
074 *   default: // violation with the new option is expected
075 *   case 2:
076 *     break;
077 * }
078 * </pre>
079 *
080 * @since 3.4
081 */
082@StatelessCheck
083public class DefaultComesLastCheck extends AbstractCheck {
084
085    /**
086     * A key is pointing to the warning message text in "messages.properties"
087     * file.
088     */
089    public static final String MSG_KEY = "default.comes.last";
090
091    /**
092     * A key is pointing to the warning message text in "messages.properties"
093     * file.
094     */
095    public static final String MSG_KEY_SKIP_IF_LAST_AND_SHARED_WITH_CASE =
096            "default.comes.last.in.casegroup";
097
098    /** Control whether to allow {@code default} along with {@code case} if they are not last. */
099    private boolean skipIfLastAndSharedWithCase;
100
101    @Override
102    public int[] getAcceptableTokens() {
103        return getRequiredTokens();
104    }
105
106    @Override
107    public int[] getDefaultTokens() {
108        return getRequiredTokens();
109    }
110
111    @Override
112    public int[] getRequiredTokens() {
113        return new int[] {
114            TokenTypes.LITERAL_DEFAULT,
115        };
116    }
117
118    /**
119     * Setter to control whether to allow {@code default} along with
120     * {@code case} if they are not last.
121     * @param newValue whether to ignore checking.
122     */
123    public void setSkipIfLastAndSharedWithCase(boolean newValue) {
124        skipIfLastAndSharedWithCase = newValue;
125    }
126
127    @Override
128    public void visitToken(DetailAST ast) {
129        final DetailAST defaultGroupAST = ast.getParent();
130        if (skipIfLastAndSharedWithCase) {
131            if (Objects.nonNull(findNextSibling(ast, TokenTypes.LITERAL_CASE))) {
132                log(ast, MSG_KEY_SKIP_IF_LAST_AND_SHARED_WITH_CASE);
133            }
134            else if (ast.getPreviousSibling() == null
135                && Objects.nonNull(findNextSibling(defaultGroupAST,
136                                                   TokenTypes.CASE_GROUP))) {
137                log(ast, MSG_KEY);
138            }
139        }
140        else if (Objects.nonNull(findNextSibling(defaultGroupAST,
141                                                 TokenTypes.CASE_GROUP))) {
142            log(ast, MSG_KEY);
143        }
144    }
145
146    /**
147     * Return token type only if passed tokenType in argument is found or returns -1.
148     *
149     * @param ast root node.
150     * @param tokenType tokentype to be processed.
151     * @return token if desired token is found or else null.
152     */
153    private static DetailAST findNextSibling(DetailAST ast, int tokenType) {
154        DetailAST token = null;
155        DetailAST node = ast.getNextSibling();
156        while (node != null) {
157            if (node.getType() == tokenType) {
158                token = node;
159                break;
160            }
161            node = node.getNextSibling();
162        }
163        return token;
164    }
165
166}