OptionalLong orElseGet() method in Java with examples

The orElseGet(java.util.function.LongSupplier) method helps us to get the value in this OptionalLong object. If a value is not present in this OptionalLong, then this method returns the result produced by the supplying function, passed as the parameter 

Syntax:

public long orElseGet(LongSupplier supplier)

Parameters: This method accepts the supplying function that produces a value to be returned. 

Return value: This method returns the long value, if present, otherwise the result produced by the supplying function. 

Exception: This method throw NullPointerException if no value is present and the supplying function is null. 

Below programs illustrate orElseGet(java.util.function.LongSupplier) method: 

Program 1:

Java

// Java program to demonstrate
// OptionalLong.orElseGet(LongSupplier) method

import java.util.OptionalLong;

public class GFG {

    public static void main(String[] args)
    {

        // create a OptionalLong
        OptionalLong oplong = OptionalLong.of(2134);

        // get value using orElseGet
        long value = oplong.orElseGet(() -> getlongValue());

        // print value
        System.out.println("value: " + value);
    }

    public static long getlongValue()
    {
        return 3242 + 123;
    }
}

Output:

value: 2134

Program 2:

Java

// Java program to demonstrate
// OptionalLong.orElseGet(LongSupplier) method

import java.util.OptionalLong;

public class GFG {

    public static void main(String[] args)
    {

        // create a OptionalLong
        OptionalLong oplong = OptionalLong.empty();

        // get value using orElseGet
        long value = oplong.orElseGet(() -> getlongValue());

        // print value
        System.out.println("value: " + value);
    }

    public static long getlongValue()
    {
        return 3242 * 234;
    }
}

Output:

value: 758628

References: https://docs.oracle.com/javase/10/docs/api/java/util/OptionalLong.html#orElseGet(java.util.function.LongSupplier)