static String removeChars ( String str , int k ) {
  int hash [ ] = new int [ MAX_CHAR ] ;
  int n = str . length ( ) ;
  for ( int i = 0 ;
  i < n ;
  ++ i ) {
    hash [ str . charAt ( i ) - 'a' ] ++ ;
  }
  String res = "" ;
  for ( int i = 0 ;
  i < n ;
  ++ i ) {
    if ( hash [ str . charAt ( i ) - 'a' ] >= k ) {
      res += str . charAt ( i ) ;
    }
  }
  return res ;
}

static String removeChars ( String str , int k ) { int hash [ ] = new int [ MAX_CHAR ] ; int n = str . length ( ) ; for ( int i = 0 ; i < n ; ++ i ) { hash [ str . charAt ( i ) - ' a ' ] ++ ; } String res = " " ; for ( int i = 0 ; i < n ; ++ i ) { if ( hash [ str . charAt ( i ) - ' a ' ] >= k ) { res += str . charAt ( i ) ; } } return res ; }
(method_declaration (modifiers) type: (type_identifier) name: (identifier) parameters: (formal_parameters (formal_parameter type: (type_identifier) name: (identifier)) (formal_parameter type: (integral_type) name: (identifier))) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) dimensions: (dimensions) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (identifier))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) 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: (identifier)) update: (update_expression (identifier)) body: (block (expression_statement (update_expression (array_access array: (identifier) index: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (character_literal))))))) (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (string_literal))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (character_literal))) right: (identifier))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))))))))) (return_statement (identifier))))