Java Guava | Longs.toArray() method with Examples
The toArray() method of Longs Class in the Guava library is used to convert the long values, passed as the parameter to this method, into a Long Array. These long values are passed as a Collection to this method. This method returns a Long array.
Syntax:
public static long[] toArray(Collection<? extends Number> collection)
Parameters: This method accepts a mandatory parameter collection which is the collection of long values to be converted in to a Long array.
Return Value: This method returns a long 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 Longs.toArray() method import com.google.common.primitives.Longs; import java.util.Arrays; import java.util.List; class GFG { // Driver's code public static void main(String[] args) { // Creating a List of Longs List<Long> myList = Arrays.asList(1L, 2L, 3L, 4L, 5L); // Using Longs.toArray() method to convert // a List or Set of Long to an array of Long long [] arr = Longs.toArray(myList); // Displaying an array containing each // value of collection, // converted to a long value System.out.println(Arrays.toString(arr)); } } |
[1, 2, 3, 4, 5]
Example 2 :
// Java code to show implementation of // Guava's Longs.toArray() method import com.google.common.primitives.Longs; import java.util.Arrays; import java.util.List; class GFG { // Driver's code public static void main(String[] args) { try { // Creating a List of Longs List<Long> myList = Arrays.asList(2L, 4L, null ); // Using Longs.toArray() method // to convert a List or Set of Long // to an array of Long. // This should raise "NullPointerException" // as the collection contains "null" // as an element long [] arr = Longs.toArray(myList); // Displaying an array containing each // value of collection, // converted to a long value System.out.println(Arrays .toString(arr)); } catch (Exception e) { System.out.println(e); } } } |
java.lang.NullPointerException
Reference: https://google.github.io/guava/releases/21.0/api/docs/com/google/common/primitives/Longs.html#toArray-java.util.Collection-
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