Java Frappe: Optional<T>

The Optional object in Java (java.util.Optional) is a container object which may or may not have a value. Designed specifically to handle the null case in a safe and explicit way, the optionals help write more readable code.

Typical Usage

1) When returning an object that might be null

   public Optional<Employee> findEmployeeByName(String name) {
     Employee employee = repo.findEmployee(name);
     return Optional.ofNullable(employee);
   }

2) To fallback upon receiving null

• Return a default object
  

  Employee employee = findEmployeeByName("John")
                        .orElse(new Employee("Unknown", 20));
  

• Return after a pipeline of operators
  

   Integer salary = findEmployeeByName("John")
                        .map(Employee::getSalary)
                        .orElse(30);
  

• Run a callback if value exists
  

   findEmployeeByName("John")
              .ifPresent(employee -> {
                  kafkaTemplate.send("employee-key", employee, "employee-topic");
              });
  

• Return an exception
  

   try {
      value = opDouble.orElseThrow(IOException::new);
   } catch (IOException e) {
      System.out.println("Exception " + e);
   }
  

  By default returns NoSuchElementException, if no value exists within the Optional.