What is the OptionalInt.orElseThrow method in Java?

In Java, the OptionalInt object is a container object that may or may not contain an integer value.

The OptionalInt class is present in the java.util package.

The orElseThrow method will return the integer value present in the OptionalInt object. If the value is not present, then the supplier function passed as an argument is executed and an exception that was returned on the function is thrown.

Syntax

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

Argument

The argument is the function to be executed if the OptionalInt object is emptyno value is present in the OptionalInt object. The supplier function should return the exception to be thrown.

Return value

If the OptionalInt object contains a value then the value is returned. Otherwise, the exception that was returned by the supplier function is returned.

This method throws NullPointerException if no value is present and the supplier function is null.

Code

The code below denotes how to use the orElseThrow method.

import java.util.OptionalInt;
  
class OptionalIntOrElseThrowExample {
    public static void main(String[] args) throws Exception{
        OptionalInt optional1 = OptionalInt.of(1);
        System.out.println("Optional1 : " + optional1);
        int val =  optional1.orElseThrow(()-> {
                return new Exception("no value present in Optional object"); 
            });
        System.out.println("Value at Optional1 is : " + val);
        OptionalInt optional2 = OptionalInt.empty();
        System.out.println("\nOptional2 : " + optional2);
        val =  optional2.orElseThrow(()-> {
                return new Exception("no value present in Optional object");
            });
    }
}

Explanation

In the code above:

In line 1, we imported the OptionalInt class.
In line 5, we created an OptionalInt object with a value of 1 using the of method.
In line 7, we called the orElseThrow method on the optional1 object. For the orElseThrow method a supplier function that returns an Exception object is passed as an argument. This method returns 1 because the optional1 object contains the value.
In line 12, we used the empty method to get an empty OptionalInt object. The returned object doesn’t have any value.
In line 13, we called the orElseThrow method on the optional2 object. For the orElseThrow method, a supplier function that returns an Exception object is passed as an argument. This method throws the exception returned by the supplier function because the optional2 object doesn’t have a value.

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