Java Guava | Bytes.toArray() method with Examples - GeeksforGeeks

31 Jan, 2019
The toArray() method of Bytes Class in the Guava library is used to convert the byte values, passed as the parameter to this method, into a Byte Array. These byte values are passed as a Collection to this method. This method returns a Byte array.
Syntax:
public static byte[] toArray(Collection<? extends Number> collection)
Parameters: This method accepts a mandatory parameter collection which is the collection of byte values to be converted in to a Byte array.
Return Value: This method returns a byte 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 Bytes.toArray() method  import com.google.common.primitives.Bytes;import java.util.Arrays;import java.util.List;  class GFG {      // Driver's code    public static void main(String[] args)    {          // Creating a List of Bytes        List<Byte> myList            = Arrays.asList((byte)1,                            (byte)2,                            (byte)3,                            (byte)4,                            (byte)5);          // Using Bytes.toArray() method to convert        // a List or Set of Byte to an array        // of Byte        byte[] arr = Bytes.toArray(myList);          // Displaying an array containing each        // value of collection,        // converted to a byte value        System.out.println(Arrays.toString(arr));    }}
[1, 2, 3, 4, 5]

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

Reference: https://google.github.io/guava/releases/19.0/api/docs/com/google/common/primitives/Bytes.html#toArray(java.util.Collection)
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