Java Guava | Doubles.toArray() method with Examples

The toArray() method of Doubles Class in the Guava library is used to convert the double values, passed as the parameter to this method, into a Double Array. These double values are passed as a Collection to this method. This method returns a Double array.

Syntax:

public static double[] toArray(Collection<? extends Number> collection)

Parameters: This method accepts a mandatory parameter collection which is the collection of double values to be converted in to a Double array.

Return Value: This method returns a double array containing the same values as a collection, in the same order.

Exceptions: This method throws NullPointerException if the passed collection or any of its elements is null.

Below programs illustrate the use of toArray() method:

Example 1 :

// Java code to show implementation of 
// Guava's Doubles.toArray() method 

import com.google.common.primitives.Doubles; 

import java.util.Arrays; 

import java.util.List; 

class GFG { 

    // Driver's code 

    public static void main(String[] args) 

    { 

        // Creating a List of Doubles 

        List<Double> myList 

            = Arrays.asList(1.2, 2.3, 3.4, 4.5, 5.6); 

        // Using Doubles.toArray() method to convert 

        // a List or Set of Double to an array of Double 

        double[] arr = Doubles.toArray(myList); 

        // Displaying an array containing each 

        // value of collection, 

        // converted to a double value 

        System.out.println(Arrays.toString(arr)); 

    } 
}

Output:

[1.2, 2.3, 3.4, 4.5, 5.6]

Example 2 :

// Java code to show implementation of 
// Guava's Doubles.toArray() method 

import com.google.common.primitives.Doubles; 

import java.util.Arrays; 

import java.util.List; 

class GFG { 

    // Driver's code 

    public static void main(String[] args) 

    { 

        try { 

            // Creating a List of Doubles 

            List<Double> myList 

                = Arrays.asList(1.2, 2.3, 3.4, null); 

            // Using Doubles.toArray() method 

            // to convert a List or Set of Double 

            // to an array of Double. 

            // This should raise "NullPointerException" 

            // as the collection contains "null" 

            // as an element 

            double[] arr = Doubles.toArray(myList); 

            // Displaying an array containing each 

            // value of collection, 

            // converted to a double value 

            System.out.println(Arrays 

                                   .toString(arr)); 

        } 

        catch (Exception e) { 

            System.out.println(e); 

        } 

    } 
}