Java 8 Optional orElseThrow() Example | Throw Exception in Optional in Java 8

1. introduction

In this tutorial, We'll learn how to throw an exception if the option is empty. Optional API orElseThrow() method returns value from Optional if present. Otherwise, it will throw the exception created by the Supplier.

2. Syntax

public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier)
                                    throws X extends Throwable

Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.

A method reference to the exception constructor with an empty argument list can be used as the supplier. For example, IllegalStateException::new, ArithmeticException::new

Java Program to Convert Degree Celsius to Kelvin & Kelvin to Celsius

1. Overview

In this tutorial, We'll learn how to convert Degree Celsius to kelvin in Java programming language. First, we will learn the formula and temperature conversion programs in java.

Degree celsius and kelvin are part of temparature mesures.

The formula for conversion:

K = ( °C + 273.15 )

Where K is kelvin and °C is degree celsius

Example 1:

Celsius: 100
Kelvin: 373.15

Example 2:

Celsius: 120
Kelvin: 393.15