Java 8 optional class | java optional class interview questions | java 8 interview | okay java
Java 8 optional | optional class | optional class interview questions | java 8 interview | okay java
Java 8 Optional class
Optional.empty()
Optional.of()
Optional.ofNullable()
.isPresent()
.ifPresent()
.get()
.orElse()
.orElseGet()
orElse v/s orElseGet()
.orElseThrow()
.filter()
.map()
.flatMap()
What is optional in java 8 ?
Optional is Final class in Java 8
to handle values as ‘available’ or ‘not available’ instead of checking null values.
What are the different ways to create an optional object
Optional.empty()
Optional.of()
Optional.ofNullable()
Optional.of() v/s Optional.ofNullable()
What is difference b/w Optional.of() and Optional.ofNullable() ?
Optional.of does not handle the "null" value , it gives null pointer exception.
.isPresent()
Boolean function
Returns true if there is a value present, otherwise false.
.get()
If a value is present in this Optional, returns the value, otherwise throws NoSuchElementException.
. ifPresent(consumer)
if a value is present, it invokes the specified consumer with the value, otherwise does nothing.
opStr2.ifPresent(s -> System.out.println(s.toUpperCase()));
. orElseThrow(supplier)
Returns the contained value, if present, otherwise throws an exception to be created by the provided supplier.
// orElseThrow
Optional < Integer > item = Optional.empty();
. filter(predicate)
If a value is present and the value matches a given predicate, it returns an Optional describing the value, otherwise returns an empty Optional.
// Filter - apply a predicate
Optional Integer age = Optional.of(20);
int a = age.filter(n -> n > 18).get();
System.out.println(a);
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