static int getOddOccurrence ( int arr [ ] , int n ) {
  HashMap < Integer , Integer > hmap = new HashMap < > ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    if ( hmap . containsKey ( arr [ i ] ) ) {
      int val = hmap . get ( arr [ i ] ) ;
      hmap . put ( arr [ i ] , val + 1 ) ;
    }
    else hmap . put ( arr [ i ] , 1 ) ;
  }
  for ( Integer a : hmap . keySet ( ) ) {
    if ( hmap . get ( a ) % 2 != 0 ) return a ;
  }
  return - 1 ;
}

static int getOddOccurrence ( int arr [ ] , int n ) { HashMap < Integer , Integer > hmap = new HashMap < > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { if ( hmap . containsKey ( arr [ i ] ) ) { int val = hmap . get ( arr [ i ] ) ; hmap . put ( arr [ i ] , val + 1 ) ; } else hmap . put ( arr [ i ] , 1 ) ; } for ( Integer a : hmap . keySet ( ) ) { if ( hmap . get ( a ) % 2 != 0 ) return a ; } return - 1 ; }
(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 (if_statement condition: (parenthesized_expression (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (identifier))))) consequence: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (identifier)))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (identifier)) (binary_expression left: (identifier) right: (decimal_integer_literal)))))) alternative: (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (identifier)) (decimal_integer_literal))))))) (enhanced_for_statement type: (type_identifier) name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (decimal_integer_literal)) right: (decimal_integer_literal))) consequence: (return_statement (identifier))))) (return_statement (unary_expression operand: (decimal_integer_literal)))))