static boolean isValid ( Set < Character > chars , char c1 , char c2 ) {
  return ( c1 == '@' && chars . contains ( c2 ) ) || ( c2 == '@' && chars . contains ( c1 ) ) || ( c1 == c2 ) ;
}

static boolean isValid ( Set < Character > chars , char c1 , char c2 ) { return ( c1 == ' @ ' && chars . contains ( c2 ) ) || ( c2 == ' @ ' && chars . contains ( c1 ) ) || ( c1 == c2 ) ; }
(method_declaration (modifiers) type: (boolean_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (generic_type (type_identifier) (type_arguments (type_identifier))) name: (identifier)) (formal_parameter type: (integral_type) name: (identifier)) (formal_parameter type: (integral_type) name: (identifier))) body: (block (return_statement (binary_expression left: (binary_expression left: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (character_literal)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))))) right: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (character_literal)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))))) right: (parenthesized_expression (binary_expression left: (identifier) right: (identifier)))))))