Java Guava | Doubles.toArray() method with Examples

Last Updated : 31 Jan, 2019

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); 
        } 
    } 
} 