Java8 - OptionalDouble class Example

#What is java.util.OptionalDouble in java?

OptionalDouble class is introduced in java8.

This is Optional container for double values that may contains empty or non empty values. if double value is present, isPresent() method returns true, and getAsDouble() method returns double value.

OptionalDouble is a primitive double version of the Optional class whereas Optional<Double> is an Optional class for Double Object.

#OptionalDouble class Example

This is an usage of isPresent(), getAsDouble(), orElse() and Lambda expressions example.

• Created OptionalDouble using static of() method

• Check double value exists or not using isPresent()method

• getAsDouble() method returns double value from an object.

• orElse() returned value if exists, return other

• ifPresent() method takes DoubleConsumer if value exists, else nothing.

import java.util.OptionalDouble;
public class OptionalDoubleDemo {
    public static void main(String[] args) {
        OptionalDouble optionalDouble = OptionalDouble.of(12.0);
        System.out.println(optionalDouble.isPresent()); // true
        System.out.println(optionalDouble.getAsDouble()); //12.0
        System.out.println(optionalDouble.orElse(12.0));//12.0
        optionalDouble.ifPresent(System.out::println);//12.0
        optionalDouble.ifPresent((value) -> System.out.println(value));//12.0
    }
}

The output of the above code execution is

true
12.0
12.0
12.0
12.0

#How to convert Double to OptionalDouble in java?

OptionalDouble of() method used to create OptionalDouble with non empty values. Syntax is public static OptionalDouble of(double value)

This takes double Value as input and returns OptionalDouble object.

import java.util.OptionalDouble;
public class Test {
    public static void main(String[] args) {
        double doubleValue = 14.3;
        OptionalDouble optionDouble = OptionalDouble.of(doubleValue);
        System.out.println(optionDouble.isPresent()); // returns true
    }
}

#How to convert OptionalDouble to double in java8?

getAsDouble() method is used to convert from OptionalDouble to double value

import java.util.OptionalDouble;
public class Test {
    public static void main(String[] args) {
        double doubleValue=0;
        OptionalDouble optionDouble = OptionalDouble.of(37.8);
        if(optionDouble.isPresent()) {
            doubleValue=optionDouble.getAsDouble();
        }
        System.out.println(doubleValue);
    }
}

#Find an Average of an array of numbers using OptionalDouble Example

This is an example of finding the average of an array of numbers in java8.

IntStream is a sequential class used to process primitive numbers with support parallel aggregation operations.

It has average() which returns OptionalDouble class. The below example uses OptionalDouble.isPresent and getAsDouble method usage a with lambda expression.

import java.util.Arrays;
import java.util.OptionalDouble;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class Test {
    public static void main(String[] args) {
        Integer[] numbersArray = {1,2,3,4,5,6,7};
        Stream<Integer> streamIntegers = Arrays.stream(numbersArray);
        IntStream intStreamNumber = streamIntegers.mapToInt(value -> value);
        OptionalDouble numberAverage = intStreamNumber.average();
        System.out.println(numberAverage.isPresent() ?
                "Numbers Average = " + numberAverage.getAsDouble() :
                "Empty Array");
    }
}

Numbers Average = 4.0

#Difference between OptionalDouble and Optional Double in java8?

Optional<Double> get() method returns Double Object OptionalDouble.getAsDouble() method returns double primitive value DoubleStream and OptionalDouble objects of double value might result nullpointerexception Optional<Double> and Stream<Double> for double value added extra wrapper to avoid null exceptions.

#OptionalDouble Methods

An optional double class has many utility methods to test values are available or not available.

#Conclusion

In this tutorial, Learned about OptionalDouble class in java

• multiple conversion examples
• Difference between OptionalDouble and Optional<Double> in java8
• OptionalDouble Methods