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Ints toArray() function | Guava | Java
  • Last Updated : 15 Nov, 2018

Guava’s Ints.toArray() returns an array containing each value of collection, converted to a int value in the manner of Number.intValue()

Syntax:

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

Parameters: This method takes the collection as parameter which is a collection of Number instances.

Return Value: This method returns an array containing the same values as collection, in the same order, converted to primitives.

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



Below examples illustrate the Ints.toArray() method:

Example 1:




// Java code to show implementation of
// Guava's Ints.toArray() method
  
import com.google.common.primitives.Ints;
import java.util.Arrays;
import java.util.List;
  
class GFG {
  
    // Driver's code
    public static void main(String[] args)
    {
  
        // Creating a List of Integers
        List<Integer>
            myList = Arrays.asList(1, 2, 3, 4, 5);
  
        // Using Ints.toArray() method to convert
        // a List or Set of Integer to an array
        // of Int
        int[] arr = Ints.toArray(myList);
  
        // Displaying an array containing each
        // value of collection,
        // converted to a int value
        System.out.println("Array from given List: "
                           + Arrays.toString(arr));
    }
}


Output:

Array from given List: [1, 2, 3, 4, 5]

Example 2: To demonstrate NullPointerException




// Java code to show implementation of
// Guava's Ints.toArray() method
  
import com.google.common.primitives.Ints;
import java.util.Arrays;
import java.util.List;
  
class GFG {
  
    // Driver's code
    public static void main(String[] args)
    {
  
        try {
  
            // Creating a List of Integers
            List<Integer>
                myList = Arrays.asList(2, 4, null);
  
            // Using Ints.toArray() method to convert
            // a List or Set of Integer to an array
            // of Int. This should raise "NullPointerException"
            // as the collection contains "null" as an element
            int[] arr = Ints.toArray(myList);
  
            // Displaying an array containing each
            // value of collection, converted to a int value
            System.out.println(Arrays.toString(arr));
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}


Output:

Exception: java.lang.NullPointerException

Reference: https://google.github.io/guava/releases/22.0/api/docs/com/google/common/primitives/Ints.html#toArray-java.util.Collection-

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