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.coding;
  
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.Set;
  import java.util.stream.Collectors;
  
  import com.puppycrawl.tools.checkstyle.StatelessCheck;
  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.FullIdent;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  import com.puppycrawl.tools.checkstyle.utils.AnnotationUtil;
  import com.puppycrawl.tools.checkstyle.utils.CheckUtil;
  
  /**
   * <p>
   * Checks that specified types are not declared to be thrown.
   * Declaring that a method throws {@code java.lang.Error} or
   * {@code java.lang.RuntimeException} is almost never acceptable.
   * </p>
   * <ul>
   * <li>
   * Property {@code illegalClassNames} - Specify throw class names to reject.
   * Type is {@code java.lang.String[]}.
   * Default value is {@code Error, RuntimeException, Throwable, java.lang.Error,
   * java.lang.RuntimeException, java.lang.Throwable}.
   * </li>
   * <li>
   * Property {@code ignoredMethodNames} - Specify names of methods to ignore.
   * Type is {@code java.lang.String[]}.
   * Default value is {@code finalize}.
   * </li>
   * <li>
   * Property {@code ignoreOverriddenMethods} - allow to ignore checking overridden methods
   * (marked with {@code Override} or {@code java.lang.Override} annotation).
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * </ul>
   * <p>
   * To configure the check:
   * </p>
   * <pre>
   * &lt;module name="IllegalThrows"/&gt;
   * </pre>
   * <p>Example:</p>
   * <pre>
   * public class Test {
   *   public void func1() throws RuntimeException {} // violation
   *   public void func2() throws Exception {}  // ok
   *   public void func3() throws Error {}  // violation
   *   public void func4() throws Throwable {} // violation
   *   public void func5() throws NullPointerException {} // ok
   *   &#064;Override
   *   public void toString() throws Error {} // ok
   * }
   * </pre>
   * <p>
   * To configure the check rejecting throws NullPointerException from methods:
   * </p>
   * <pre>
   * &lt;module name="IllegalThrows"&gt;
   *   &lt;property name="illegalClassNames" value="NullPointerException"/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>Example:</p>
   * <pre>
   * public class Test {
   *   public void func1() throws RuntimeException {} // ok
   *   public void func2() throws Exception {}  // ok
   *   public void func3() throws Error {}  // ok
   *   public void func4() throws Throwable {} // ok
   *   public void func5() throws NullPointerException {} // violation
   *   &#064;Override
   *   public void toString() throws Error {} // ok
   * }
   * </pre>
   * <p>
   * To configure the check ignoring method named "func1()":
   * </p>
   * <pre>
   * &lt;module name="IllegalThrows"&gt;
   *   &lt;property name="ignoredMethodNames" value="func1"/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>Example:</p>
   * <pre>
   * public class Test {
   *   public void func1() throws RuntimeException {} // ok
   *   public void func2() throws Exception {}  // ok
   *   public void func3() throws Error {}  // violation
   *   public void func4() throws Throwable {} // violation
   *   public void func5() throws NullPointerException {} // ok
   *   &#064;Override
   *   public void toString() throws Error {} // ok
   * }
   * </pre>
   * <p>
   * To configure the check to warn on overridden methods:
   * </p>
   * <pre>
   * &lt;module name=&quot;IllegalThrows&quot;&gt;
   *   &lt;property name=&quot;ignoreOverriddenMethods&quot; value=&quot;false&quot;/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>Example:</p>
   * <pre>
   * public class Test {
   *   public void func1() throws RuntimeException {} // violation
   *   public void func2() throws Exception {}  // ok
   *   public void func3() throws Error {}  // violation
   *   public void func4() throws Throwable {} // violation
   *   public void func5() throws NullPointerException {} // ok
   *   &#064;Override
   *   public void toString() throws Error {} // violation
   * }
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code illegal.throw}
   * </li>
   * </ul>
   *
   * @since 4.0
   */
  @StatelessCheck
  public final class IllegalThrowsCheck extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY = "illegal.throw";
  
      /** Specify names of methods to ignore. */
      private final Set<String> ignoredMethodNames =
          Arrays.stream(new String[] {"finalize", }).collect(Collectors.toCollection(HashSet::new));
  
      /** Specify throw class names to reject. */
      private final Set<String> illegalClassNames = Arrays.stream(
          new String[] {"Error", "RuntimeException", "Throwable", "java.lang.Error",
                        "java.lang.RuntimeException", "java.lang.Throwable", })
          .collect(Collectors.toCollection(HashSet::new));
  
      /**
       * Allow to ignore checking overridden methods (marked with {@code Override}
       * or {@code java.lang.Override} annotation).
       */
      private boolean ignoreOverriddenMethods = true;
  
      /**
       * Setter to specify throw class names to reject.
       *
       * @param classNames
       *            array of illegal exception classes
       */
      public void setIllegalClassNames(final String... classNames) {
          illegalClassNames.clear();
          illegalClassNames.addAll(
                  CheckUtil.parseClassNames(classNames));
      }
  
      @Override
      public int[] getDefaultTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return new int[] {TokenTypes.LITERAL_THROWS};
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public void visitToken(DetailAST detailAST) {
          final DetailAST methodDef = detailAST.getParent();
          // Check if the method with the given name should be ignored.
          if (!isIgnorableMethod(methodDef)) {
              DetailAST token = detailAST.getFirstChild();
              while (token != null) {
                  final FullIdent ident = FullIdent.createFullIdent(token);
                  final String identText = ident.getText();
                  if (illegalClassNames.contains(identText)) {
                      log(token, MSG_KEY, identText);
                  }
                  token = token.getNextSibling();
              }
          }
      }
  
      /**
       * Checks if current method is ignorable due to Check's properties.
       *
       * @param methodDef {@link TokenTypes#METHOD_DEF METHOD_DEF}
       * @return true if method is ignorable.
       */
      private boolean isIgnorableMethod(DetailAST methodDef) {
          return shouldIgnoreMethod(methodDef.findFirstToken(TokenTypes.IDENT).getText())
              || ignoreOverriddenMethods
                 && AnnotationUtil.hasOverrideAnnotation(methodDef);
      }
  
      /**
       * Check if the method is specified in the ignore method list.
       *
       * @param name the name to check
       * @return whether the method with the passed name should be ignored
       */
      private boolean shouldIgnoreMethod(String name) {
          return ignoredMethodNames.contains(name);
      }
  
      /**
       * Setter to specify names of methods to ignore.
       *
       * @param methodNames array of ignored method names
       */
      public void setIgnoredMethodNames(String... methodNames) {
          ignoredMethodNames.clear();
          Collections.addAll(ignoredMethodNames, methodNames);
      }
  
      /**
       * Setter to allow to ignore checking overridden methods
       * (marked with {@code Override} or {@code java.lang.Override} annotation).
       *
       * @param ignoreOverriddenMethods Check's property.
       */
      public void setIgnoreOverriddenMethods(boolean ignoreOverriddenMethods) {
          this.ignoreOverriddenMethods = ignoreOverriddenMethods;
      }
  
  }
  