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 that method type parameter names conform to a specified pattern.
028 * </p>
029 * <ul>
030 * <li>
031 * Property {@code format} - Specifies valid identifiers.
032 * Type is {@code java.util.regex.Pattern}.
033 * Default value is {@code "^[A-Z]$"}.
034 * </li>
035 * </ul>
036 * <p>
037 * To configure the check:
038 * </p>
039 * <pre>
040 * &lt;module name=&quot;MethodTypeParameterName&quot;/&gt;
041 * </pre>
042 * <p>Code Example:</p>
043 * <pre>
044 * class MyClass {
045 *   public &lt;T&gt; void method1() {} // OK
046 *   public &lt;a&gt; void method2() {} // violation,  name 'a' must match pattern '^[A-Z]$'
047 *   public &lt;K, V&gt; void method3() {} // OK
048 *   public &lt;k, V&gt; void method4() {} // violation, name 'k' must match pattern '^[A-Z]$'
049 * }
050 * </pre>
051 * <p>
052 * An example of how to configure the check for names that are only a single letter is:
053 * </p>
054 * <pre>
055 * &lt;module name=&quot;MethodTypeParameterName&quot;&gt;
056 *    &lt;property name=&quot;format&quot; value=&quot;^[a-zA-Z]$&quot;/&gt;
057 * &lt;/module&gt;
058 * </pre>
059 * <p>Code Example:</p>
060 * <pre>
061 * class MyClass {
062 *   public &lt;T&gt; void method1() {} // OK
063 *   public &lt;a&gt; void method2() {} // OK
064 *   public &lt;K, V&gt; void method3() {} // OK
065 *   public &lt;k, V&gt; void method4() {} // OK
066 * }
067 * </pre>
068 * <p>
069 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
070 * </p>
071 * <p>
072 * Violation Message Keys:
073 * </p>
074 * <ul>
075 * <li>
076 * {@code name.invalidPattern}
077 * </li>
078 * </ul>
079 *
080 * @since 5.0
081 */
082public class MethodTypeParameterNameCheck
083    extends AbstractNameCheck {
084
085    /** Creates a new {@code MethodTypeParameterNameCheck} instance. */
086    public MethodTypeParameterNameCheck() {
087        super("^[A-Z]$");
088    }
089
090    @Override
091    public int[] getDefaultTokens() {
092        return getRequiredTokens();
093    }
094
095    @Override
096    public int[] getAcceptableTokens() {
097        return getRequiredTokens();
098    }
099
100    @Override
101    public int[] getRequiredTokens() {
102        return new int[] {
103            TokenTypes.TYPE_PARAMETER,
104        };
105    }
106
107    @Override
108    protected final boolean mustCheckName(DetailAST ast) {
109        final DetailAST location =
110            ast.getParent().getParent();
111        return location.getType() == TokenTypes.METHOD_DEF;
112    }
113
114}