Java8 - OptionalDouble class Example


java.util.OptionalDouble

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. getAsDouble() method returns double value.
OptionalDouble is a primitive double version of Optional class whereas Optional is an Optional class for Double Object.

OptionalDouble Example

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

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 java8?

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.

double doubleValue = 14.3;  
OptionalDouble optionDouble = OptionalDouble.of(doubleValue);  
System.out.println(optionDouble.isPresent()); // returns true  

How to convert OptionalDouble to Double in java8?

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

OptionalDouble optionDouble = OptionalDouble.of(37.8);  
  if(optionDouble.isPresent()) {  
   doubleValue=optionDouble.getAsDouble();  
  }  
  System.out.println(doubleValue);  

IntStream Average example 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.

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 in java8?

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

Methods

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

Method

Description

empty()

Creating Empty OptionalDouble Instance

getAsDouble()

Return double value, if value exists in OptionDouble, Else NoSuchElementException

ifPresent(DoubleConsumer consumer)

Executes DoubleConsumer, if value exists in OptionDouble, else do nothing

isPresent()

Returns true, if value exists in OptionDouble, else returns false

of(Double double)

Creation of OptionalDouble with non null values, if null is passed, NullPointerException thrown and OptionDouble object will not be initlized

orElse(double other)

Return default value if value is not presented in OptionalDouble

orElseGet(DoubleSupplier other)

Returns value if value presented in OptionalDouble, else supplier is being called and result this will be returned

orElseThrow(Supplier exceptionSupplier)

Returns value if value presented in OptionalDouble, else supplier is being called and throws an error

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