static int totalPairs ( int arr [ ] , int n ) {
  HashMap < Integer , Integer > m = new HashMap < > ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    int count = countSetBits ( arr [ i ] ) ;
    if ( m . containsKey ( count ) ) m . put ( count , m . get ( count ) + 1 ) ;
    else m . put ( count , 1 ) ;
  }
  int result = 0 ;
  for ( Map . Entry < Integer , Integer > entry : m . entrySet ( ) ) {
    int value = entry . getValue ( ) ;
    result += ( ( value * ( value - 1 ) ) / 2 ) ;
  }
  return result ;
}

static int totalPairs ( int arr [ ] , int n ) { HashMap < Integer , Integer > m = new HashMap < > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { int count = countSetBits ( arr [ i ] ) ; if ( m . containsKey ( count ) ) m . put ( count , m . get ( count ) + 1 ) ; else m . put ( count , 1 ) ; } int result = 0 ; for ( Map . Entry < Integer , Integer > entry : m . entrySet ( ) ) { int value = entry . getValue ( ) ; result += ( ( value * ( value - 1 ) ) / 2 ) ; } return result ; }
(method_declaration (modifiers) type: (integral_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) (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: (identifier)) update: (update_expression (identifier)) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (identifier)))))) (if_statement condition: (parenthesized_expression (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) consequence: (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (decimal_integer_literal))))) alternative: (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (decimal_integer_literal))))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (enhanced_for_statement type: (generic_type (scoped_type_identifier (type_identifier) (type_identifier)) (type_arguments (type_identifier) (type_identifier))) name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (expression_statement (assignment_expression left: (identifier) right: (parenthesized_expression (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))))) right: (decimal_integer_literal))))))) (return_statement (identifier))))