///////////////////////////////////////////////////////////////////////////////////////////////
   // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
   // Copyright (C) 2001-2024 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.ArrayDeque;
  import java.util.BitSet;
  import java.util.Deque;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Optional;
  
  import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
  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.CheckUtil;
  import com.puppycrawl.tools.checkstyle.utils.ScopeUtil;
  import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
  
  /**
   * <p>
   * Checks that local variables that never have their values changed are declared final.
   * The check can be configured to also check that unchanged parameters are declared final.
   * </p>
   * <p>
   * When configured to check parameters, the check ignores parameters of interface
   * methods and abstract methods.
   * </p>
   * <ul>
   * <li>
   * Property {@code validateEnhancedForLoopVariable} - Control whether to check
   * <a href="https://docs.oracle.com/javase/specs/jls/se11/html/jls-14.html#jls-14.14.2">
   * enhanced for-loop</a> variable.
   * Type is {@code boolean}.
   * Default value is {@code false}.
   * </li>
   * <li>
   * Property {@code validateUnnamedVariables} - Control whether to check
   * <a href="https://docs.oracle.com/javase/specs/jls/se21/preview/specs/unnamed-jls.html">
   * unnamed variables</a>.
   * Type is {@code boolean}.
   * Default value is {@code false}.
   * </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#VARIABLE_DEF">
   * VARIABLE_DEF</a>.
   * </li>
   * </ul>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code final.variable}
   * </li>
   * </ul>
   *
   * @since 3.2
   */
  @FileStatefulCheck
  public class FinalLocalVariableCheck extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY = "final.variable";
  
      /**
       * Assign operator types.
       */
      private static final BitSet ASSIGN_OPERATOR_TYPES = TokenUtil.asBitSet(
          TokenTypes.POST_INC,
          TokenTypes.POST_DEC,
         TokenTypes.ASSIGN,
         TokenTypes.PLUS_ASSIGN,
         TokenTypes.MINUS_ASSIGN,
         TokenTypes.STAR_ASSIGN,
         TokenTypes.DIV_ASSIGN,
         TokenTypes.MOD_ASSIGN,
         TokenTypes.SR_ASSIGN,
         TokenTypes.BSR_ASSIGN,
         TokenTypes.SL_ASSIGN,
         TokenTypes.BAND_ASSIGN,
         TokenTypes.BXOR_ASSIGN,
         TokenTypes.BOR_ASSIGN,
         TokenTypes.INC,
         TokenTypes.DEC
     );
 
     /**
      * Loop types.
      */
     private static final BitSet LOOP_TYPES = TokenUtil.asBitSet(
         TokenTypes.LITERAL_FOR,
         TokenTypes.LITERAL_WHILE,
         TokenTypes.LITERAL_DO
     );
 
     /** Scope Deque. */
     private final Deque<ScopeData> scopeStack = new ArrayDeque<>();
 
     /** Assigned variables of current scope. */
     private final Deque<Deque<DetailAST>> currentScopeAssignedVariables =
             new ArrayDeque<>();
 
     /**
      * Control whether to check
      * <a href="https://docs.oracle.com/javase/specs/jls/se11/html/jls-14.html#jls-14.14.2">
      * enhanced for-loop</a> variable.
      */
     private boolean validateEnhancedForLoopVariable;
 
     /**
      * Control whether to check
      * <a href="https://docs.oracle.com/javase/specs/jls/se21/preview/specs/unnamed-jls.html">
      * unnamed variables</a>.
      */
     private boolean validateUnnamedVariables;
 
     /**
      * Setter to control whether to check
      * <a href="https://docs.oracle.com/javase/specs/jls/se11/html/jls-14.html#jls-14.14.2">
      * enhanced for-loop</a> variable.
      *
      * @param validateEnhancedForLoopVariable whether to check for-loop variable
      * @since 6.5
      */
     public final void setValidateEnhancedForLoopVariable(boolean validateEnhancedForLoopVariable) {
         this.validateEnhancedForLoopVariable = validateEnhancedForLoopVariable;
     }
 
     /**
      * Setter to control whether to check
      * <a href="https://docs.oracle.com/javase/specs/jls/se21/preview/specs/unnamed-jls.html">
      * unnamed variables</a>.
      *
      * @param validateUnnamedVariables whether to check unnamed variables
      * @since 10.18.0
      */
     public final void setValidateUnnamedVariables(boolean validateUnnamedVariables) {
         this.validateUnnamedVariables = validateUnnamedVariables;
     }
 
     @Override
     public int[] getRequiredTokens() {
         return new int[] {
             TokenTypes.IDENT,
             TokenTypes.CTOR_DEF,
             TokenTypes.METHOD_DEF,
             TokenTypes.SLIST,
             TokenTypes.OBJBLOCK,
             TokenTypes.LITERAL_BREAK,
             TokenTypes.LITERAL_FOR,
             TokenTypes.EXPR,
         };
     }
 
     @Override
     public int[] getDefaultTokens() {
         return new int[] {
             TokenTypes.IDENT,
             TokenTypes.CTOR_DEF,
             TokenTypes.METHOD_DEF,
             TokenTypes.SLIST,
             TokenTypes.OBJBLOCK,
             TokenTypes.LITERAL_BREAK,
             TokenTypes.LITERAL_FOR,
             TokenTypes.VARIABLE_DEF,
             TokenTypes.EXPR,
         };
     }
 
     @Override
     public int[] getAcceptableTokens() {
         return new int[] {
             TokenTypes.IDENT,
             TokenTypes.CTOR_DEF,
             TokenTypes.METHOD_DEF,
             TokenTypes.SLIST,
             TokenTypes.OBJBLOCK,
             TokenTypes.LITERAL_BREAK,
             TokenTypes.LITERAL_FOR,
             TokenTypes.VARIABLE_DEF,
             TokenTypes.PARAMETER_DEF,
             TokenTypes.EXPR,
         };
     }
 
     // -@cs[CyclomaticComplexity] The only optimization which can be done here is moving CASE-block
     // expressions to separate methods, but that will not increase readability.
     @Override
     public void visitToken(DetailAST ast) {
         switch (ast.getType()) {
             case TokenTypes.OBJBLOCK:
             case TokenTypes.METHOD_DEF:
             case TokenTypes.CTOR_DEF:
             case TokenTypes.LITERAL_FOR:
                 scopeStack.push(new ScopeData());
                 break;
             case TokenTypes.SLIST:
                 currentScopeAssignedVariables.push(new ArrayDeque<>());
                 if (ast.getParent().getType() != TokenTypes.CASE_GROUP
                     || ast.getParent().getParent().findFirstToken(TokenTypes.CASE_GROUP)
                     == ast.getParent()) {
                     storePrevScopeUninitializedVariableData();
                     scopeStack.push(new ScopeData());
                 }
                 break;
             case TokenTypes.PARAMETER_DEF:
                 if (!isInLambda(ast)
                         && ast.findFirstToken(TokenTypes.MODIFIERS)
                             .findFirstToken(TokenTypes.FINAL) == null
                         && !isInAbstractOrNativeMethod(ast)
                         && !ScopeUtil.isInInterfaceBlock(ast)
                         && !isMultipleTypeCatch(ast)
                         && !CheckUtil.isReceiverParameter(ast)) {
                     insertParameter(ast);
                 }
                 break;
             case TokenTypes.VARIABLE_DEF:
                 if (ast.getParent().getType() != TokenTypes.OBJBLOCK
                         && ast.findFirstToken(TokenTypes.MODIFIERS)
                             .findFirstToken(TokenTypes.FINAL) == null
                         && !isVariableInForInit(ast)
                         && shouldCheckEnhancedForLoopVariable(ast)
                         && shouldCheckUnnamedVariable(ast)) {
                     insertVariable(ast);
                 }
                 break;
             case TokenTypes.IDENT:
                 final int parentType = ast.getParent().getType();
                 if (isAssignOperator(parentType) && isFirstChild(ast)) {
                     final Optional<FinalVariableCandidate> candidate = getFinalCandidate(ast);
                     if (candidate.isPresent()) {
                         determineAssignmentConditions(ast, candidate.orElseThrow());
                         currentScopeAssignedVariables.peek().add(ast);
                     }
                     removeFinalVariableCandidateFromStack(ast);
                 }
                 break;
             case TokenTypes.LITERAL_BREAK:
                 scopeStack.peek().containsBreak = true;
                 break;
             case TokenTypes.EXPR:
                 // Switch labeled expression has no slist
                 if (ast.getParent().getType() == TokenTypes.SWITCH_RULE) {
                     storePrevScopeUninitializedVariableData();
                 }
                 break;
             default:
                 throw new IllegalStateException("Incorrect token type");
         }
     }
 
     @Override
     public void leaveToken(DetailAST ast) {
         Map<String, FinalVariableCandidate> scope = null;
         final DetailAST parentAst = ast.getParent();
         switch (ast.getType()) {
             case TokenTypes.OBJBLOCK:
             case TokenTypes.CTOR_DEF:
             case TokenTypes.METHOD_DEF:
             case TokenTypes.LITERAL_FOR:
                 scope = scopeStack.pop().scope;
                 break;
             case TokenTypes.EXPR:
                 // Switch labeled expression has no slist
                 if (parentAst.getType() == TokenTypes.SWITCH_RULE
                     && shouldUpdateUninitializedVariables(parentAst)) {
                     updateAllUninitializedVariables();
                 }
                 break;
             case TokenTypes.SLIST:
                 boolean containsBreak = false;
                 if (parentAst.getType() != TokenTypes.CASE_GROUP
                     || findLastCaseGroupWhichContainsSlist(parentAst.getParent()) == parentAst) {
                     containsBreak = scopeStack.peek().containsBreak;
                     scope = scopeStack.pop().scope;
                 }
                 if (containsBreak || shouldUpdateUninitializedVariables(parentAst)) {
                     updateAllUninitializedVariables();
                 }
                 updateCurrentScopeAssignedVariables();
                 break;
             default:
                 // do nothing
         }
         if (scope != null) {
             for (FinalVariableCandidate candidate : scope.values()) {
                 final DetailAST ident = candidate.variableIdent;
                 log(ident, MSG_KEY, ident.getText());
             }
         }
     }
 
     /**
      * Update assigned variables in a temporary stack.
      */
     private void updateCurrentScopeAssignedVariables() {
         // -@cs[MoveVariableInsideIf] assignment value is a modification call, so it can't be moved
         final Deque<DetailAST> poppedScopeAssignedVariableData =
                 currentScopeAssignedVariables.pop();
         final Deque<DetailAST> currentScopeAssignedVariableData =
                 currentScopeAssignedVariables.peek();
         if (currentScopeAssignedVariableData != null) {
             currentScopeAssignedVariableData.addAll(poppedScopeAssignedVariableData);
         }
     }
 
     /**
      * Determines identifier assignment conditions (assigned or already assigned).
      *
      * @param ident identifier.
      * @param candidate final local variable candidate.
      */
     private static void determineAssignmentConditions(DetailAST ident,
                                                       FinalVariableCandidate candidate) {
         if (candidate.assigned) {
             final int[] blockTypes = {
                 TokenTypes.LITERAL_ELSE,
                 TokenTypes.CASE_GROUP,
                 TokenTypes.SWITCH_RULE,
             };
             if (!isInSpecificCodeBlocks(ident, blockTypes)) {
                 candidate.alreadyAssigned = true;
             }
         }
         else {
             candidate.assigned = true;
         }
     }
 
     /**
      * Checks whether the scope of a node is restricted to a specific code blocks.
      *
      * @param node node.
      * @param blockTypes int array of all block types to check.
      * @return true if the scope of a node is restricted to specific code block types.
      */
     private static boolean isInSpecificCodeBlocks(DetailAST node, int... blockTypes) {
         boolean returnValue = false;
         for (int blockType : blockTypes) {
             for (DetailAST token = node; token != null; token = token.getParent()) {
                 final int type = token.getType();
                 if (type == blockType) {
                     returnValue = true;
                     break;
                 }
             }
         }
         return returnValue;
     }
 
     /**
      * Gets final variable candidate for ast.
      *
      * @param ast ast.
      * @return Optional of {@link FinalVariableCandidate} for ast from scopeStack.
      */
     private Optional<FinalVariableCandidate> getFinalCandidate(DetailAST ast) {
         Optional<FinalVariableCandidate> result = Optional.empty();
         final Iterator<ScopeData> iterator = scopeStack.descendingIterator();
         while (iterator.hasNext() && result.isEmpty()) {
             final ScopeData scopeData = iterator.next();
             result = scopeData.findFinalVariableCandidateForAst(ast);
         }
         return result;
     }
 
     /**
      * Store un-initialized variables in a temporary stack for future use.
      */
     private void storePrevScopeUninitializedVariableData() {
         final ScopeData scopeData = scopeStack.peek();
         final Deque<DetailAST> prevScopeUninitializedVariableData =
                 new ArrayDeque<>();
         scopeData.uninitializedVariables.forEach(prevScopeUninitializedVariableData::push);
         scopeData.prevScopeUninitializedVariables = prevScopeUninitializedVariableData;
     }
 
     /**
      * Update current scope data uninitialized variable according to the whole scope data.
      */
     private void updateAllUninitializedVariables() {
         final boolean hasSomeScopes = !currentScopeAssignedVariables.isEmpty();
         if (hasSomeScopes) {
             scopeStack.forEach(scopeData -> {
                 updateUninitializedVariables(scopeData.prevScopeUninitializedVariables);
             });
         }
     }
 
     /**
      * Update current scope data uninitialized variable according to the specific scope data.
      *
      * @param scopeUninitializedVariableData variable for specific stack of uninitialized variables
      */
     private void updateUninitializedVariables(Deque<DetailAST> scopeUninitializedVariableData) {
         final Iterator<DetailAST> iterator = currentScopeAssignedVariables.peek().iterator();
         while (iterator.hasNext()) {
             final DetailAST assignedVariable = iterator.next();
             boolean shouldRemove = false;
             for (DetailAST variable : scopeUninitializedVariableData) {
                 for (ScopeData scopeData : scopeStack) {
                     final FinalVariableCandidate candidate =
                         scopeData.scope.get(variable.getText());
                     DetailAST storedVariable = null;
                     if (candidate != null) {
                         storedVariable = candidate.variableIdent;
                     }
                     if (storedVariable != null
                             && isSameVariables(assignedVariable, variable)) {
                         scopeData.uninitializedVariables.push(variable);
                         shouldRemove = true;
                     }
                 }
             }
             if (shouldRemove) {
                 iterator.remove();
             }
         }
     }
 
     /**
      * If there is an {@code else} following or token is CASE_GROUP or
      * SWITCH_RULE and there is another {@code case} following, then update the
      * uninitialized variables.
      *
      * @param ast token to be checked
      * @return true if should be updated, else false
      */
     private static boolean shouldUpdateUninitializedVariables(DetailAST ast) {
         return ast.getLastChild().getType() == TokenTypes.LITERAL_ELSE
             || isCaseTokenWithAnotherCaseFollowing(ast);
     }
 
     /**
      * If token is CASE_GROUP or SWITCH_RULE and there is another {@code case} following.
      *
      * @param ast token to be checked
      * @return true if token is CASE_GROUP or SWITCH_RULE and there is another {@code case}
      *     following, else false
      */
     private static boolean isCaseTokenWithAnotherCaseFollowing(DetailAST ast) {
         boolean result = false;
         if (ast.getType() == TokenTypes.CASE_GROUP) {
             result = findLastCaseGroupWhichContainsSlist(ast.getParent()) != ast;
         }
         else if (ast.getType() == TokenTypes.SWITCH_RULE) {
             result = ast.getNextSibling().getType() == TokenTypes.SWITCH_RULE;
         }
         return result;
     }
 
     /**
      * Returns the last token of type {@link TokenTypes#CASE_GROUP} which contains
      * {@link TokenTypes#SLIST}.
      *
      * @param literalSwitchAst ast node of type {@link TokenTypes#LITERAL_SWITCH}
      * @return the matching token, or null if no match
      */
     private static DetailAST findLastCaseGroupWhichContainsSlist(DetailAST literalSwitchAst) {
         DetailAST returnValue = null;
         for (DetailAST astIterator = literalSwitchAst.getFirstChild(); astIterator != null;
              astIterator = astIterator.getNextSibling()) {
             if (astIterator.findFirstToken(TokenTypes.SLIST) != null) {
                 returnValue = astIterator;
             }
         }
         return returnValue;
     }
 
     /**
      * Determines whether enhanced for-loop variable should be checked or not.
      *
      * @param ast The ast to compare.
      * @return true if enhanced for-loop variable should be checked.
      */
     private boolean shouldCheckEnhancedForLoopVariable(DetailAST ast) {
         return validateEnhancedForLoopVariable
                 || ast.getParent().getType() != TokenTypes.FOR_EACH_CLAUSE;
     }
 
     /**
      * Determines whether unnamed variable should be checked or not.
      *
      * @param ast The ast to compare.
      * @return true if unnamed variable should be checked.
      */
     private boolean shouldCheckUnnamedVariable(DetailAST ast) {
         return validateUnnamedVariables
                  || !"_".equals(ast.findFirstToken(TokenTypes.IDENT).getText());
     }
 
     /**
      * Insert a parameter at the topmost scope stack.
      *
      * @param ast the variable to insert.
      */
     private void insertParameter(DetailAST ast) {
         final Map<String, FinalVariableCandidate> scope = scopeStack.peek().scope;
         final DetailAST astNode = ast.findFirstToken(TokenTypes.IDENT);
         scope.put(astNode.getText(), new FinalVariableCandidate(astNode));
     }
 
     /**
      * Insert a variable at the topmost scope stack.
      *
      * @param ast the variable to insert.
      */
     private void insertVariable(DetailAST ast) {
         final Map<String, FinalVariableCandidate> scope = scopeStack.peek().scope;
         final DetailAST astNode = ast.findFirstToken(TokenTypes.IDENT);
         final FinalVariableCandidate candidate = new FinalVariableCandidate(astNode);
         // for-each variables are implicitly assigned
         candidate.assigned = ast.getParent().getType() == TokenTypes.FOR_EACH_CLAUSE;
         scope.put(astNode.getText(), candidate);
         if (!isInitialized(astNode)) {
             scopeStack.peek().uninitializedVariables.add(astNode);
         }
     }
 
     /**
      * Check if VARIABLE_DEF is initialized or not.
      *
      * @param ast VARIABLE_DEF to be checked
      * @return true if initialized
      */
     private static boolean isInitialized(DetailAST ast) {
         return ast.getParent().getLastChild().getType() == TokenTypes.ASSIGN;
     }
 
     /**
      * Whether the ast is the first child of its parent.
      *
      * @param ast the ast to check.
      * @return true if the ast is the first child of its parent.
      */
     private static boolean isFirstChild(DetailAST ast) {
         return ast.getPreviousSibling() == null;
     }
 
     /**
      * Removes the final variable candidate from the Stack.
      *
      * @param ast variable to remove.
      */
     private void removeFinalVariableCandidateFromStack(DetailAST ast) {
         final Iterator<ScopeData> iterator = scopeStack.descendingIterator();
         while (iterator.hasNext()) {
             final ScopeData scopeData = iterator.next();
             final Map<String, FinalVariableCandidate> scope = scopeData.scope;
             final FinalVariableCandidate candidate = scope.get(ast.getText());
             DetailAST storedVariable = null;
             if (candidate != null) {
                 storedVariable = candidate.variableIdent;
             }
             if (storedVariable != null && isSameVariables(storedVariable, ast)) {
                 if (shouldRemoveFinalVariableCandidate(scopeData, ast)) {
                     scope.remove(ast.getText());
                 }
                 break;
             }
         }
     }
 
     /**
      * Check if given parameter definition is a multiple type catch.
      *
      * @param parameterDefAst parameter definition
      * @return true if it is a multiple type catch, false otherwise
      */
     private static boolean isMultipleTypeCatch(DetailAST parameterDefAst) {
         final DetailAST typeAst = parameterDefAst.findFirstToken(TokenTypes.TYPE);
         return typeAst.findFirstToken(TokenTypes.BOR) != null;
     }
 
     /**
      * Whether the final variable candidate should be removed from the list of final local variable
      * candidates.
      *
      * @param scopeData the scope data of the variable.
      * @param ast the variable ast.
      * @return true, if the variable should be removed.
      */
     private static boolean shouldRemoveFinalVariableCandidate(ScopeData scopeData, DetailAST ast) {
         boolean shouldRemove = true;
         for (DetailAST variable : scopeData.uninitializedVariables) {
             if (variable.getText().equals(ast.getText())) {
                 // if the variable is declared outside the loop and initialized inside
                 // the loop, then it cannot be declared final, as it can be initialized
                 // more than once in this case
                 final DetailAST currAstLoopAstParent = getParentLoop(ast);
                 final DetailAST currVarLoopAstParent = getParentLoop(variable);
                 if (currAstLoopAstParent == currVarLoopAstParent) {
                     final FinalVariableCandidate candidate = scopeData.scope.get(ast.getText());
                     shouldRemove = candidate.alreadyAssigned;
                 }
                 scopeData.uninitializedVariables.remove(variable);
                 break;
             }
         }
         return shouldRemove;
     }
 
     /**
      * Get the ast node of type {@link FinalVariableCandidate#LOOP_TYPES} that is the ancestor
      * of the current ast node, if there is no such node, null is returned.
      *
      * @param ast ast node
      * @return ast node of type {@link FinalVariableCandidate#LOOP_TYPES} that is the ancestor
      *         of the current ast node, null if no such node exists
      */
     private static DetailAST getParentLoop(DetailAST ast) {
         DetailAST parentLoop = ast;
         while (parentLoop != null
             && !isLoopAst(parentLoop.getType())) {
             parentLoop = parentLoop.getParent();
         }
         return parentLoop;
     }
 
     /**
      * Is Arithmetic operator.
      *
      * @param parentType token AST
      * @return true is token type is in arithmetic operator
      */
     private static boolean isAssignOperator(int parentType) {
         return ASSIGN_OPERATOR_TYPES.get(parentType);
     }
 
     /**
      * Checks if current variable is defined in
      *  {@link TokenTypes#FOR_INIT for-loop init}, e.g.:
      * <p>
      * {@code
      * for (int i = 0, j = 0; i < j; i++) { . . . }
      * }
      * </p>
      * {@code i, j} are defined in {@link TokenTypes#FOR_INIT for-loop init}
      *
      * @param variableDef variable definition node.
      * @return true if variable is defined in {@link TokenTypes#FOR_INIT for-loop init}
      */
     private static boolean isVariableInForInit(DetailAST variableDef) {
         return variableDef.getParent().getType() == TokenTypes.FOR_INIT;
     }
 
     /**
      * Determines whether an AST is a descendant of an abstract or native method.
      *
      * @param ast the AST to check.
      * @return true if ast is a descendant of an abstract or native method.
      */
     private static boolean isInAbstractOrNativeMethod(DetailAST ast) {
         boolean abstractOrNative = false;
         DetailAST currentAst = ast;
         while (currentAst != null && !abstractOrNative) {
             if (currentAst.getType() == TokenTypes.METHOD_DEF) {
                 final DetailAST modifiers =
                     currentAst.findFirstToken(TokenTypes.MODIFIERS);
                 abstractOrNative = modifiers.findFirstToken(TokenTypes.ABSTRACT) != null
                         || modifiers.findFirstToken(TokenTypes.LITERAL_NATIVE) != null;
             }
             currentAst = currentAst.getParent();
         }
         return abstractOrNative;
     }
 
     /**
      * Check if current param is lambda's param.
      *
      * @param paramDef {@link TokenTypes#PARAMETER_DEF parameter def}.
      * @return true if current param is lambda's param.
      */
     private static boolean isInLambda(DetailAST paramDef) {
         return paramDef.getParent().getParent().getType() == TokenTypes.LAMBDA;
     }
 
     /**
      * Find the Class, Constructor, Enum, Method, or Field in which it is defined.
      *
      * @param ast Variable for which we want to find the scope in which it is defined
      * @return ast The Class or Constructor or Method in which it is defined.
      */
     private static DetailAST findFirstUpperNamedBlock(DetailAST ast) {
         DetailAST astTraverse = ast;
         while (!TokenUtil.isOfType(astTraverse, TokenTypes.METHOD_DEF, TokenTypes.CLASS_DEF,
                 TokenTypes.ENUM_DEF, TokenTypes.CTOR_DEF, TokenTypes.COMPACT_CTOR_DEF)
                 && !ScopeUtil.isClassFieldDef(astTraverse)) {
             astTraverse = astTraverse.getParent();
         }
         return astTraverse;
     }
 
     /**
      * Check if both the Variables are same.
      *
      * @param ast1 Variable to compare
      * @param ast2 Variable to compare
      * @return true if both the variables are same, otherwise false
      */
     private static boolean isSameVariables(DetailAST ast1, DetailAST ast2) {
         final DetailAST classOrMethodOfAst1 =
             findFirstUpperNamedBlock(ast1);
         final DetailAST classOrMethodOfAst2 =
             findFirstUpperNamedBlock(ast2);
         return classOrMethodOfAst1 == classOrMethodOfAst2 && ast1.getText().equals(ast2.getText());
     }
 
     /**
      * Checks whether the ast is a loop.
      *
      * @param ast the ast to check.
      * @return true if the ast is a loop.
      */
     private static boolean isLoopAst(int ast) {
         return LOOP_TYPES.get(ast);
     }
 
     /**
      * Holder for the scope data.
      */
     private static final class ScopeData {
 
         /** Contains variable definitions. */
         private final Map<String, FinalVariableCandidate> scope = new HashMap<>();
 
         /** Contains definitions of uninitialized variables. */
         private final Deque<DetailAST> uninitializedVariables = new ArrayDeque<>();
 
         /** Contains definitions of previous scope uninitialized variables. */
         private Deque<DetailAST> prevScopeUninitializedVariables = new ArrayDeque<>();
 
         /** Whether there is a {@code break} in the scope. */
         private boolean containsBreak;
 
         /**
          * Searches for final local variable candidate for ast in the scope.
          *
          * @param ast ast.
          * @return Optional of {@link FinalVariableCandidate}.
          */
         public Optional<FinalVariableCandidate> findFinalVariableCandidateForAst(DetailAST ast) {
             Optional<FinalVariableCandidate> result = Optional.empty();
             DetailAST storedVariable = null;
             final Optional<FinalVariableCandidate> candidate =
                 Optional.ofNullable(scope.get(ast.getText()));
             if (candidate.isPresent()) {
                 storedVariable = candidate.orElseThrow().variableIdent;
             }
             if (storedVariable != null && isSameVariables(storedVariable, ast)) {
                 result = candidate;
             }
             return result;
         }
 
     }
 
     /** Represents information about final local variable candidate. */
     private static final class FinalVariableCandidate {
 
         /** Identifier token. */
         private final DetailAST variableIdent;
         /** Whether the variable is assigned. */
         private boolean assigned;
         /** Whether the variable is already assigned. */
         private boolean alreadyAssigned;
 
         /**
          * Creates new instance.
          *
          * @param variableIdent variable identifier.
          */
         private FinalVariableCandidate(DetailAST variableIdent) {
             this.variableIdent = variableIdent;
         }
 
     }
 
 }