Java 8 Interview Questions and Answers

Optional is a container object used to contain not-null objects. Optional object is used to represent null with absent value. This class has various utility methods to facilitate code to handle values as ‘available’ or ‘not available’ instead of checking null values.

public final class Optional<T> extends Object

public class OptionalTester {

   public static void main(String args[]) {

      OptionalTester optionalTester = new OptionalTester();

      Integer value1 = null;

      Integer value2 = new Integer(10);

      //Optional.ofNullable - allows passed parameter to be null.

      Optional<Integer> a = Optional.ofNullable(value1);

      //Optional.of - throws NullPointerException if passed parameter is null

      Optional<Integer> b = Optional.of(value2);

      System.out.println(optionalTester.sum(a,b));

   }

   public Integer sum(Optional<Integer> a, Optional<Integer> b) {

      //Optional.isPresent - checks the value is present or not

      System.out.println("First parameter is present: " + a.isPresent());

      System.out.println("Second parameter is present: " + b.isPresent());

      //Optional.orElse - returns the value if present otherwise returns

      //the default value passed.

      Integer value1 = a.orElse(new Integer(0));

      //Optional.get - gets the value, value should be present

      Integer value2 = b.get();

      return value1 + value2;

   }

}

First parameter is present: false

Second parameter is present: true

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