Create new Object

All the core classes in the new API are constructed by fluent factory methods. When constructing a value by its constituent fields, the factory is called of; when converting from another type, the factory is called from. There are also parse methods that take strings as parameters. See
 
LocalDateTime timePoint = LocalDateTime.now(); // The current date and time
LocalDate.of(2012, Month.DECEMBER, 12); // from values
LocalDate.ofEpochDay(150); // middle of 1970 LocalTime.of(17, 18);
LocalTime.parse("10:15:30"); // From a String

// LocalTime java.time.LocalTime.from(TemporalAccessor temporal)
LocalDateTime timePoint2 = LocalDateTime.from(Month.DECEMBER);
System.out.println(timePoint2.toString());

Use Object

You can also alter the object values in order to perform calculations.
Because all core classes are immutable in the new API, these methods are called with and return new objects, rather than using setters (see bellow). There are also methods for calculations based on the different fields. 

 // Set the value, returning a new object
LocalDateTime thePast = timePoint.withDayOfMonth(
    10).withYear(2010);

/* You can use direct manipulation methods,
    or pass a value and field pair */
LocalDateTime yetAnother = thePast.plusWeeks(
    3).plus(3, ChronoUnit.WEEKS);
 

Reference :

https://www.oracle.com/technical-resources/articles/java/jf14-date-time.html