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.naming;
021
022import com.puppycrawl.tools.checkstyle.api.DetailAST;
023import com.puppycrawl.tools.checkstyle.api.TokenTypes;
024
025/**
026 * <p>
027 * Checks lambda parameter names.
028 * </p>
029 * <ul>
030 * <li>
031 * Property {@code format} - Specifies valid identifiers.
032 * Default value is {@code "^[a-z][a-zA-Z0-9]*$"}.
033 * </li>
034 * </ul>
035 * <p>
036 * An example of how to configure the check is:
037 * </p>
038 * <pre>
039 * &lt;module name="LambdaParameterName"/&gt;
040 * </pre>
041 * <p>Code Example:</p>
042 * <pre>
043 * Function&lt;String, String&gt; function1 = s -&gt; s.toLowerCase(); // OK
044 * Function&lt;String, String&gt; function2 = S -&gt; S.toLowerCase(); // violation, name 'S'
045 *                                                // must match pattern '^[a-z][a-zA-Z0-9]*$'
046 * </pre>
047 * <p>
048 * An example of how to configure the check for names that begin
049 * with a lower case letter, followed by letters is:
050 * </p>
051 * <pre>
052 * &lt;module name="LambdaParameterName"&gt;
053 *   &lt;property name="format" value="^[a-z]([a-zA-Z]+)*$"/&gt;
054 * &lt;/module&gt;
055 * </pre>
056 * <p>
057 * Code Example:
058 * </p>
059 * <pre>
060 * class MyClass {
061 *   Function&lt;String, String&gt; function1 = str -&gt; str.toUpperCase().trim(); // OK
062 *   Function&lt;String, String&gt; function2 = _s -&gt; _s.trim(); // violation, name '_s'
063 *                                              // must match pattern '^[a-z]([a-zA-Z]+)*$'
064 *
065 *   public boolean myMethod(String sentence) {
066 *     return Stream.of(sentence.split(" "))
067 *             .map(word -&gt; word.trim()) // OK
068 *             .anyMatch(Word -&gt; "in".equals(Word)); // violation, name 'Word'
069 *                                                      // must match pattern '^[a-z]([a-zA-Z]+)*$'
070 *   }
071 * }
072 *
073 * </pre>
074 *
075 * @since 8.11
076 */
077public class LambdaParameterNameCheck extends AbstractNameCheck {
078
079    /** Creates new instance of {@code LambdaParameterNameCheck}. */
080    public LambdaParameterNameCheck() {
081        super("^[a-z][a-zA-Z0-9]*$");
082    }
083
084    @Override
085    public int[] getDefaultTokens() {
086        return getRequiredTokens();
087    }
088
089    @Override
090    public int[] getAcceptableTokens() {
091        return getRequiredTokens();
092    }
093
094    @Override
095    public int[] getRequiredTokens() {
096        return new int[] {
097            TokenTypes.LAMBDA,
098        };
099    }
100
101    @Override
102    public void visitToken(DetailAST ast) {
103        final DetailAST parametersNode = ast.findFirstToken(TokenTypes.PARAMETERS);
104        if (parametersNode == null) {
105            super.visitToken(ast);
106        }
107        else {
108            for (DetailAST parameterDef = parametersNode.getFirstChild();
109                 parameterDef != null;
110                 parameterDef = parameterDef.getNextSibling()) {
111                if (parameterDef.getType() == TokenTypes.PARAMETER_DEF) {
112                    super.visitToken(parameterDef);
113                }
114            }
115        }
116    }
117
118    @Override
119    protected boolean mustCheckName(DetailAST ast) {
120        return true;
121    }
122
123}