code: ///////////////////////////////////////////////////////////////////////////////////////////////
  // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
  // Copyright (C) 2001-2023 the original author or authors.
  //
  // This library is free software; you can redistribute it and/or
  // modify it under the terms of the GNU Lesser General Public
  // License as published by the Free Software Foundation; either
  // version 2.1 of the License, or (at your option) any later version.
  //
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ///////////////////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle.checks.naming;
  
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  
  /**
   * <p>
   * Checks that {@code catch} parameter names conform to a specified pattern.
   * </p>
   * <p>
   * Default pattern has the following characteristic:
   * </p>
   * <ul>
   * <li>allows names beginning with two lowercase letters followed by at least one uppercase or
   * lowercase letter</li>
   * <li>allows {@code e} abbreviation (suitable for exceptions end errors)</li>
   * <li>allows {@code ex} abbreviation (suitable for exceptions)</li>
   * <li>allows {@code t} abbreviation (suitable for throwables)</li>
   * <li>prohibits numbered abbreviations like {@code e1} or {@code t2}</li>
   * <li>prohibits one letter prefixes like {@code pException}</li>
   * <li>prohibits two letter abbreviations like {@code ie} or {@code ee}</li>
   * <li>prohibits any other characters than letters</li>
   * </ul>
   * <ul>
   * <li>
   * Property {@code format} - Specifies valid identifiers.
   * Type is {@code java.util.regex.Pattern}.
   * Default value is {@code "^(e|t|ex|[a-z][a-z][a-zA-Z]+)$"}.
   * </li>
   * </ul>
   * <p>
   * To configure the check:
   * </p>
   * <pre>
   * &lt;module name="CatchParameterName"/&gt;
   * </pre>
   * <p>Example:</p>
   * <pre>
   * public class MyTest {
   *   public void myTest() {
   *     try {
   *       // ...
   *     } catch (ArithmeticException e) { // OK
   *       // ...
   *     } catch (ArrayIndexOutOfBoundsException ex) { // OK
   *       // ...
   *     } catch (Throwable t) { // OK
   *       // ...
   *     } catch (IndexOutOfBoundsException e123) { // violation, digits
   *                                // not allowed
   *       // ...
   *     } catch (NullPointerException ab) { // violation, should have at least
   *                              // three characters if not e|t|ex
   *       // ...
   *     } catch (ArrayStoreException abc) { // OK
   *       // ...
   *     } catch (InterruptedException aBC) { // violation, first two characters
   *                               // should be in lowercase
   *       // ...
   *     } catch (RuntimeException abC) { // OK
   *       // ...
   *     } catch (Exception abCD) { // OK
   *       // ...
   *     }
   *   }
   * }
   * </pre>
   * <p>
   * An example of how to configure the check for names that begin with a lower case letter,
   * followed by any letters or digits is:
   * </p>
   * <p>Configuration:</p>
   * <pre>
   * &lt;module name="CatchParameterName"&gt;
   *   &lt;property name="format" value="^[a-z][a-zA-Z0-9]+$"/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>Example:</p>
   * <pre>
   * public class MyTest {
   *   public void myTest() {
   *     try {
   *       // ...
   *     } catch (ArithmeticException ex) { // OK
   *       // ...
   *     } catch (ArrayIndexOutOfBoundsException ex2) { // OK
   *       // ...
   *     } catch (IOException thirdException) { // OK
   *       // ...
   *     } catch (Exception FourthException) { // violation, the initial letter
   *                                           // should be lowercase
   *       // ...
   *     }
   *   }
   * }
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code name.invalidPattern}
   * </li>
   * </ul>
   *
   * @since 6.14
   */
  public class CatchParameterNameCheck extends AbstractNameCheck {
  
      /**
       * Creates a new {@code CatchParameterNameCheck} instance.
       */
      public CatchParameterNameCheck() {
          super("^(e|t|ex|[a-z][a-z][a-zA-Z]+)$");
      }
  
      @Override
      public int[] getDefaultTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return new int[] {TokenTypes.PARAMETER_DEF};
      }
  
      @Override
      protected boolean mustCheckName(DetailAST ast) {
          return ast.getParent().getType() == TokenTypes.LITERAL_CATCH;
      }
  
  }
  