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.whitespace;
  
  import java.util.Optional;
  
  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.TokenTypes;
  import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
  
  /**
   * <p>
   * Checks that there is no whitespace after a token.
   * More specifically, it checks that it is not followed by whitespace,
   * or (if linebreaks are allowed) all characters on the line after are
   * whitespace. To forbid linebreaks after a token, set property
   * {@code allowLineBreaks} to {@code false}.
   * </p>
   * <p>
   * The check processes
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ARRAY_DECLARATOR">
   * ARRAY_DECLARATOR</a> and
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#INDEX_OP">
   * INDEX_OP</a> tokens specially from other tokens. Actually it is checked that
   * there is no whitespace before these tokens, not after them. Space after the
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ANNOTATIONS">
   * ANNOTATIONS</a> before
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ARRAY_DECLARATOR">
   * ARRAY_DECLARATOR</a> and
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#INDEX_OP">
   * INDEX_OP</a> will be ignored.
   * </p>
   * <p>
   * If the annotation is between the type and the array, like {@code char @NotNull [] param},
   * the check will skip validation for spaces.
   * </p>
   * <p>
   * Note: This check processes the
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#LITERAL_SYNCHRONIZED">
   * LITERAL_SYNCHRONIZED</a> token only when it appears as a part of a
   * <a href="https://docs.oracle.com/javase/specs/jls/se19/html/jls-14.html#jls-14.19">
   * synchronized statement</a>, i.e. {@code synchronized(this) {}}.
   * </p>
   * <ul>
   * <li>
   * Property {@code allowLineBreaks} - Control whether whitespace is allowed
   * if the token is at a linebreak.
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * <li>
   * Property {@code tokens} - tokens to check
   * Type is {@code java.lang.String[]}.
   * Validation type is {@code tokenSet}.
   * Default value is:
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ARRAY_INIT">
   * ARRAY_INIT</a>,
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#AT">
   * AT</a>,
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#INC">
   * INC</a>,
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#DEC">
   * DEC</a>,
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#UNARY_MINUS">
   * UNARY_MINUS</a>,
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#UNARY_PLUS">
   * UNARY_PLUS</a>,
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#BNOT">
   * BNOT</a>,
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#LNOT">
   * LNOT</a>,
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#DOT">
   * DOT</a>,
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ARRAY_DECLARATOR">
   * ARRAY_DECLARATOR</a>,
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#INDEX_OP">
   * INDEX_OP</a>.
   * </li>
   * </ul>
   * <p>
   * To configure the check:
   * </p>
   * <pre>
   * &lt;module name=&quot;NoWhitespaceAfter&quot;/&gt;
   * </pre>
   * <p>Example:</p>
   * <pre>
   * class Test {
   *
   *   public void lineBreak(String x) {
   *     Integer.
   *         parseInt(x); // Ok
   *     Integer.parseInt(x); // Ok
   *   }
   *
   *   public void dotOperator(String s) {
   *     Integer.parseInt(s); // Ok
   *     Integer. parseInt(s); // violation, '.' is followed by whitespace
   *   }
   *
   *   public void arrayDec() {
   *     int[] arr = arr; // Ok
   *     int [] arr = arr; // violation, int is followed by whitespace
   *   }
   *
   *   public void bitwiseNot(int a) {
   *     a = ~ a; // violation '~' is followed by whitespace
   *     a = ~a; // Ok
   *   }
   * }
   * </pre>
   * <p>To configure the check to forbid linebreaks after a DOT token:
   * </p>
   * <pre>
   * &lt;module name=&quot;NoWhitespaceAfter&quot;&gt;
   *   &lt;property name=&quot;tokens&quot; value=&quot;DOT&quot;/&gt;
   *   &lt;property name=&quot;allowLineBreaks&quot; value=&quot;false&quot;/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>Example:</p>
   * <pre>
   * class Test {
   *
   *   public void lineBreak(String x) {
   *     Integer.
   *         parseInt(x); // violation, '.' is followed by whitespace
   *     Integer.parseInt(x); // Ok
   *   }
   *
   *   public void dotOperator(String s) {
   *     Integer.parseInt(s); // Ok
   *     Integer. parseInt(s); // violation, '.' is followed by whitespace
   *   }
   *
   *   public void arrayDec() {
   *     int[] arr = arr; // Ok
   *     int [] arr = arr; // Ok
   *   }
   *
   *   public void bitwiseNot(int a) {
   *     a = ~ a; // Ok
   *     a = ~a; // Ok
   *   }
   * }
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code ws.followed}
   * </li>
   * </ul>
   *
   * @since 3.0
   */
  @StatelessCheck
  public class NoWhitespaceAfterCheck extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY = "ws.followed";
  
      /** Control whether whitespace is allowed if the token is at a linebreak. */
      private boolean allowLineBreaks = true;
  
      @Override
      public int[] getDefaultTokens() {
          return new int[] {
              TokenTypes.ARRAY_INIT,
              TokenTypes.AT,
              TokenTypes.INC,
              TokenTypes.DEC,
              TokenTypes.UNARY_MINUS,
              TokenTypes.UNARY_PLUS,
              TokenTypes.BNOT,
              TokenTypes.LNOT,
              TokenTypes.DOT,
              TokenTypes.ARRAY_DECLARATOR,
              TokenTypes.INDEX_OP,
          };
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return new int[] {
              TokenTypes.ARRAY_INIT,
              TokenTypes.AT,
              TokenTypes.INC,
              TokenTypes.DEC,
              TokenTypes.UNARY_MINUS,
              TokenTypes.UNARY_PLUS,
              TokenTypes.BNOT,
              TokenTypes.LNOT,
              TokenTypes.DOT,
              TokenTypes.TYPECAST,
              TokenTypes.ARRAY_DECLARATOR,
              TokenTypes.INDEX_OP,
              TokenTypes.LITERAL_SYNCHRONIZED,
              TokenTypes.METHOD_REF,
          };
      }
  
      @Override
      public int[] getRequiredTokens() {
          return CommonUtil.EMPTY_INT_ARRAY;
      }
  
      /**
       * Setter to control whether whitespace is allowed if the token is at a linebreak.
       *
       * @param allowLineBreaks whether whitespace should be
       *     flagged at linebreaks.
       */
      public void setAllowLineBreaks(boolean allowLineBreaks) {
          this.allowLineBreaks = allowLineBreaks;
      }
  
      @Override
      public void visitToken(DetailAST ast) {
          if (shouldCheckWhitespaceAfter(ast)) {
              final DetailAST whitespaceFollowedAst = getWhitespaceFollowedNode(ast);
              final int whitespaceColumnNo = getPositionAfter(whitespaceFollowedAst);
              final int whitespaceLineNo = whitespaceFollowedAst.getLineNo();
  
              if (hasTrailingWhitespace(ast, whitespaceColumnNo, whitespaceLineNo)) {
                  log(ast, MSG_KEY, whitespaceFollowedAst.getText());
              }
          }
      }
  
      /**
       * For a visited ast node returns node that should be checked
       * for not being followed by whitespace.
       *
       * @param ast
       *        , visited node.
       * @return node before ast.
       */
      private static DetailAST getWhitespaceFollowedNode(DetailAST ast) {
          final DetailAST whitespaceFollowedAst;
          switch (ast.getType()) {
              case TokenTypes.TYPECAST:
                  whitespaceFollowedAst = ast.findFirstToken(TokenTypes.RPAREN);
                  break;
              case TokenTypes.ARRAY_DECLARATOR:
                  whitespaceFollowedAst = getArrayDeclaratorPreviousElement(ast);
                  break;
              case TokenTypes.INDEX_OP:
                  whitespaceFollowedAst = getIndexOpPreviousElement(ast);
                  break;
              default:
                  whitespaceFollowedAst = ast;
          }
          return whitespaceFollowedAst;
      }
  
      /**
       * Returns whether whitespace after a visited node should be checked. For example, whitespace
       * is not allowed between a type and an array declarator (returns true), except when there is
       * an annotation in between the type and array declarator (returns false).
       *
       * @param ast the visited node
       * @return true if whitespace after ast should be checked
       */
      private static boolean shouldCheckWhitespaceAfter(DetailAST ast) {
          final DetailAST previousSibling = ast.getPreviousSibling();
          final boolean isSynchronizedMethod = ast.getType() == TokenTypes.LITERAL_SYNCHRONIZED
                          && ast.getFirstChild() == null;
          return !isSynchronizedMethod
                  && (previousSibling == null || previousSibling.getType() != TokenTypes.ANNOTATIONS);
      }
  
      /**
       * Gets position after token (place of possible redundant whitespace).
       *
       * @param ast Node representing token.
       * @return position after token.
       */
      private static int getPositionAfter(DetailAST ast) {
          final int after;
          // If target of possible redundant whitespace is in method definition.
          if (ast.getType() == TokenTypes.IDENT
                  && ast.getNextSibling() != null
                  && ast.getNextSibling().getType() == TokenTypes.LPAREN) {
              final DetailAST methodDef = ast.getParent();
              final DetailAST endOfParams = methodDef.findFirstToken(TokenTypes.RPAREN);
              after = endOfParams.getColumnNo() + 1;
          }
          else {
              after = ast.getColumnNo() + ast.getText().length();
          }
          return after;
      }
  
      /**
       * Checks if there is unwanted whitespace after the visited node.
       *
       * @param ast
       *        , visited node.
       * @param whitespaceColumnNo
       *        , column number of a possible whitespace.
       * @param whitespaceLineNo
       *        , line number of a possible whitespace.
       * @return true if whitespace found.
       */
      private boolean hasTrailingWhitespace(DetailAST ast,
          int whitespaceColumnNo, int whitespaceLineNo) {
          final boolean result;
          final int astLineNo = ast.getLineNo();
          final int[] line = getLineCodePoints(astLineNo - 1);
          if (astLineNo == whitespaceLineNo && whitespaceColumnNo < line.length) {
              result = CommonUtil.isCodePointWhitespace(line, whitespaceColumnNo);
          }
          else {
              result = !allowLineBreaks;
          }
          return result;
      }
  
      /**
       * Returns proper argument for getPositionAfter method, it is a token after
       * {@link TokenTypes#ARRAY_DECLARATOR ARRAY_DECLARATOR}, in can be {@link TokenTypes#RBRACK
       * RBRACK}, {@link TokenTypes#IDENT IDENT} or an array type definition (literal).
       *
       * @param ast
       *        , {@link TokenTypes#ARRAY_DECLARATOR ARRAY_DECLARATOR} node.
       * @return previous node by text order.
       * @throws IllegalStateException if an unexpected token type is encountered.
       */
      private static DetailAST getArrayDeclaratorPreviousElement(DetailAST ast) {
          final DetailAST previousElement;
  
          if (ast.getPreviousSibling() != null
                  && ast.getPreviousSibling().getType() == TokenTypes.ARRAY_DECLARATOR) {
              // Covers higher dimension array declarations and initializations
              previousElement = getPreviousElementOfMultiDimArray(ast);
          }
          else {
              // first array index, is preceded with identifier or type
              final DetailAST parent = ast.getParent();
              switch (parent.getType()) {
                  // generics
                  case TokenTypes.TYPE_UPPER_BOUNDS:
                  case TokenTypes.TYPE_LOWER_BOUNDS:
                      previousElement = ast.getPreviousSibling();
                      break;
                  case TokenTypes.LITERAL_NEW:
                  case TokenTypes.TYPE_ARGUMENT:
                  case TokenTypes.DOT:
                      previousElement = getTypeLastNode(ast);
                      break;
                  // mundane array declaration, can be either java style or C style
                  case TokenTypes.TYPE:
                      previousElement = getPreviousNodeWithParentOfTypeAst(ast, parent);
                      break;
                  // java 8 method reference
                  case TokenTypes.METHOD_REF:
                      final DetailAST ident = getIdentLastToken(ast);
                      if (ident == null) {
                          // i.e. int[]::new
                          previousElement = ast.getParent().getFirstChild();
                      }
                      else {
                          previousElement = ident;
                      }
                      break;
                  default:
                      throw new IllegalStateException("unexpected ast syntax " + parent);
              }
          }
          return previousElement;
      }
  
      /**
       * Gets the previous element of a second or higher dimension of an
       * array declaration or initialization.
       *
       * @param leftBracket the token to get previous element of
       * @return the previous element
       */
      private static DetailAST getPreviousElementOfMultiDimArray(DetailAST leftBracket) {
          final DetailAST previousRightBracket = leftBracket.getPreviousSibling().getLastChild();
  
          DetailAST ident = null;
          // This will get us past the type ident, to the actual identifier
          DetailAST parent = leftBracket.getParent().getParent();
          while (ident == null) {
              ident = parent.findFirstToken(TokenTypes.IDENT);
              parent = parent.getParent();
          }
  
          final DetailAST previousElement;
          if (ident.getColumnNo() > previousRightBracket.getColumnNo()
                  && ident.getColumnNo() < leftBracket.getColumnNo()) {
              // C style and Java style ' int[] arr []' in same construct
              previousElement = ident;
          }
          else {
              // 'int[][] arr' or 'int arr[][]'
              previousElement = previousRightBracket;
          }
          return previousElement;
      }
  
      /**
       * Gets previous node for {@link TokenTypes#INDEX_OP INDEX_OP} token
       * for usage in getPositionAfter method, it is a simplified copy of
       * getArrayDeclaratorPreviousElement method.
       *
       * @param ast
       *        , {@link TokenTypes#INDEX_OP INDEX_OP} node.
       * @return previous node by text order.
       */
      private static DetailAST getIndexOpPreviousElement(DetailAST ast) {
          final DetailAST result;
          final DetailAST firstChild = ast.getFirstChild();
          if (firstChild.getType() == TokenTypes.INDEX_OP) {
              // second or higher array index
              result = firstChild.findFirstToken(TokenTypes.RBRACK);
          }
          else if (firstChild.getType() == TokenTypes.IDENT) {
              result = firstChild;
          }
          else {
              final DetailAST ident = getIdentLastToken(ast);
              if (ident == null) {
                  final DetailAST rparen = ast.findFirstToken(TokenTypes.RPAREN);
                  // construction like new int[]{1}[0]
                  if (rparen == null) {
                      final DetailAST lastChild = firstChild.getLastChild();
                      result = lastChild.findFirstToken(TokenTypes.RCURLY);
                  }
                  // construction like ((byte[]) pixels)[0]
                  else {
                      result = rparen;
                  }
              }
              else {
                  result = ident;
              }
          }
          return result;
      }
  
      /**
       * Searches parameter node for a type node.
       * Returns it or its last node if it has an extended structure.
       *
       * @param ast
       *        , subject node.
       * @return type node.
       */
      private static DetailAST getTypeLastNode(DetailAST ast) {
          final DetailAST typeLastNode;
          final DetailAST parent = ast.getParent();
          final boolean isPrecededByTypeArgs =
                  parent.findFirstToken(TokenTypes.TYPE_ARGUMENTS) != null;
          final Optional<DetailAST> objectArrayType = Optional.ofNullable(getIdentLastToken(ast));
  
          if (isPrecededByTypeArgs) {
              typeLastNode = parent.findFirstToken(TokenTypes.TYPE_ARGUMENTS)
                      .findFirstToken(TokenTypes.GENERIC_END);
          }
          else if (objectArrayType.isPresent()) {
              typeLastNode = objectArrayType.get();
          }
          else {
              typeLastNode = parent.getFirstChild();
          }
  
          return typeLastNode;
      }
  
      /**
       * Finds previous node by text order for an array declarator,
       * which parent type is {@link TokenTypes#TYPE TYPE}.
       *
       * @param ast
       *        , array declarator node.
       * @param parent
       *        , its parent node.
       * @return previous node by text order.
       */
      private static DetailAST getPreviousNodeWithParentOfTypeAst(DetailAST ast, DetailAST parent) {
          final DetailAST previousElement;
          final DetailAST ident = getIdentLastToken(parent.getParent());
          final DetailAST lastTypeNode = getTypeLastNode(ast);
          // sometimes there are ident-less sentences
          // i.e. "(Object[]) null", but in casual case should be
          // checked whether ident or lastTypeNode has preceding position
          // determining if it is java style or C style
  
          if (ident == null || ident.getLineNo() > ast.getLineNo()) {
              previousElement = lastTypeNode;
          }
          else if (ident.getLineNo() < ast.getLineNo()) {
              previousElement = ident;
          }
          // ident and lastTypeNode lay on one line
          else {
              final int instanceOfSize = 13;
              // +2 because ast has `[]` after the ident
              if (ident.getColumnNo() >= ast.getColumnNo() + 2
                  // +13 because ident (at most 1 character) is followed by
                  // ' instanceof ' (12 characters)
                  || lastTypeNode.getColumnNo() >= ident.getColumnNo() + instanceOfSize) {
                  previousElement = lastTypeNode;
              }
              else {
                  previousElement = ident;
              }
          }
          return previousElement;
      }
  
      /**
       * Gets leftmost token of identifier.
       *
       * @param ast
       *        , token possibly possessing an identifier.
       * @return leftmost token of identifier.
       */
      private static DetailAST getIdentLastToken(DetailAST ast) {
          final DetailAST result;
          final Optional<DetailAST> dot = getPrecedingDot(ast);
          // method call case
          if (dot.isEmpty() || ast.getFirstChild().getType() == TokenTypes.METHOD_CALL) {
              final DetailAST methodCall = ast.findFirstToken(TokenTypes.METHOD_CALL);
              if (methodCall == null) {
                  result = ast.findFirstToken(TokenTypes.IDENT);
              }
              else {
                  result = methodCall.findFirstToken(TokenTypes.RPAREN);
              }
          }
          // qualified name case
          else {
              result = dot.get().getFirstChild().getNextSibling();
          }
          return result;
      }
  
      /**
       * Gets the dot preceding a class member array index operation or class
       * reference.
       *
       * @param leftBracket the ast we are checking
       * @return dot preceding the left bracket
       */
      private static Optional<DetailAST> getPrecedingDot(DetailAST leftBracket) {
          final DetailAST referencedMemberDot = leftBracket.findFirstToken(TokenTypes.DOT);
          final Optional<DetailAST> result = Optional.ofNullable(referencedMemberDot);
          return result.or(() -> getReferencedClassDot(leftBracket));
      }
  
      /**
       * Gets the dot preceding a class reference.
       *
       * @param leftBracket the ast we are checking
       * @return dot preceding the left bracket
       */
      private static Optional<DetailAST> getReferencedClassDot(DetailAST leftBracket) {
          final DetailAST parent = leftBracket.getParent();
          Optional<DetailAST> classDot = Optional.empty();
          if (parent.getType() != TokenTypes.ASSIGN) {
              classDot = Optional.ofNullable(parent.findFirstToken(TokenTypes.DOT));
          }
          return classDot;
      }
  }
  