static boolean checkDuplicatesWithinK ( int arr [ ] , int k ) {
  HashSet < Integer > set = new HashSet < > ( ) ;
  for ( int i = 0 ;
  i < arr . length ;
  i ++ ) {
    if ( set . contains ( arr [ i ] ) ) return true ;
    set . add ( arr [ i ] ) ;
    if ( i >= k ) set . remove ( arr [ i - k ] ) ;
  }
  return false ;
}

static boolean checkDuplicatesWithinK ( int arr [ ] , int k ) { HashSet < Integer > set = new HashSet < > ( ) ; for ( int i = 0 ; i < arr . length ; i ++ ) { if ( set . contains ( arr [ i ] ) ) return true ; set . add ( arr [ i ] ) ; if ( i >= k ) set . remove ( arr [ i - k ] ) ; } return false ; }
(method_declaration (modifiers) type: (boolean_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (integral_type) name: (identifier) dimensions: (dimensions)) (formal_parameter type: (integral_type) name: (identifier))) body: (block (local_variable_declaration type: (generic_type (type_identifier) (type_arguments (type_identifier))) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (generic_type (type_identifier) (type_arguments)) arguments: (argument_list)))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (field_access object: (identifier) field: (identifier))) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (identifier))))) consequence: (return_statement (true))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (identifier))))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (binary_expression left: (identifier) right: (identifier))))))))) (return_statement (false))))