001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2020 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.design;
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;
026import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
027import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
028
029/**
030 * <p>
031 * Checks that each top-level class, interface, enum
032 * or annotation resides in a source file of its own.
033 * Official description of a 'top-level' term:
034 * <a href="https://docs.oracle.com/javase/specs/jls/se11/html/jls-7.html#jls-7.6">
035 * 7.6. Top Level Type Declarations</a>. If file doesn't contains
036 * public class, interface, enum or annotation, top-level type is the first type in file.
037 * </p>
038 * <p>
039 * To configure the check:
040 * </p>
041 * <pre>
042 * &lt;module name=&quot;OneTopLevelClass&quot;/&gt;
043 * </pre>
044 * <p>
045 * <b>ATTENTION:</b> This Check does not support customization of validated tokens,
046 * so do not use the "tokens" property.
047 * </p>
048 * <p>
049 * An example of code with violations:
050 * </p>
051 * <pre>
052 * public class Foo { // OK, first top-level class
053 *   // methods
054 * }
055 *
056 * class Foo2 { // violation, second top-level class
057 *   // methods
058 * }
059 * </pre>
060 * <p>
061 * An example of code without public top-level type:
062 * </p>
063 * <pre>
064 * class Foo { // OK, first top-level class
065 *   // methods
066 * }
067 *
068 * class Foo2 { // violation, second top-level class
069 *   // methods
070 * }
071 * </pre>
072 * <p>
073 * An example of code without violations:
074 * </p>
075 * <pre>
076 * public class Foo { // OK, only one top-level class
077 *   // methods
078 * }
079 * </pre>
080 * <p>
081 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
082 * </p>
083 * <p>
084 * Violation Message Keys:
085 * </p>
086 * <ul>
087 * <li>
088 * {@code one.top.level.class}
089 * </li>
090 * </ul>
091 *
092 * @since 5.8
093 */
094@StatelessCheck
095public class OneTopLevelClassCheck extends AbstractCheck {
096
097    /**
098     * A key is pointing to the warning message text in "messages.properties"
099     * file.
100     */
101    public static final String MSG_KEY = "one.top.level.class";
102
103    @Override
104    public int[] getDefaultTokens() {
105        return getRequiredTokens();
106    }
107
108    @Override
109    public int[] getAcceptableTokens() {
110        return getRequiredTokens();
111    }
112
113    // ZERO tokens as Check do Traverse of Tree himself, he does not need to subscribed to Tokens
114    @Override
115    public int[] getRequiredTokens() {
116        return CommonUtil.EMPTY_INT_ARRAY;
117    }
118
119    @Override
120    public void beginTree(DetailAST rootAST) {
121        DetailAST currentNode = rootAST;
122        boolean publicTypeFound = false;
123        DetailAST firstType = null;
124
125        while (currentNode != null) {
126            if (isTypeDef(currentNode)) {
127                if (isPublic(currentNode)) {
128                    // log the first type later
129                    publicTypeFound = true;
130                }
131                if (firstType == null) {
132                    // first type is set aside
133                    firstType = currentNode;
134                }
135                else if (!isPublic(currentNode)) {
136                    // extra non-public type, log immediately
137                    final String typeName = currentNode
138                        .findFirstToken(TokenTypes.IDENT).getText();
139                    log(currentNode, MSG_KEY, typeName);
140                }
141            }
142            currentNode = currentNode.getNextSibling();
143        }
144
145        // if there was a public type and first type is non-public, log it
146        if (publicTypeFound && !isPublic(firstType)) {
147            final String typeName = firstType
148                .findFirstToken(TokenTypes.IDENT).getText();
149            log(firstType, MSG_KEY, typeName);
150        }
151    }
152
153    /**
154     * Checks if an AST node is a type definition.
155     *
156     * @param node AST node to check.
157     * @return true if the node is a type (class, enum, interface, annotation) definition.
158     */
159    private static boolean isTypeDef(DetailAST node) {
160        return TokenUtil.isTypeDeclaration(node.getType());
161    }
162
163    /**
164     * Checks if a type is public.
165     *
166     * @param typeDef type definition node.
167     * @return true if a type has a public access level modifier.
168     */
169    private static boolean isPublic(DetailAST typeDef) {
170        final DetailAST modifiers =
171                typeDef.findFirstToken(TokenTypes.MODIFIERS);
172        return modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) != null;
173    }
174
175}