Java Guava | Bytes.toArray() method with Examples

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

// 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));
    }
}

Output:

[1, 2, 3, 4, 5]

Example 2:

Java

// 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);
        }
    }
}

Output:

java.lang.NullPointerException

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

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