Demonstrate the concept of Threads to achieve multitasking program using Thread class and Runnable Interface (separately) for the below scenario:

Create an Array of 9 numbers. And create three Threads to split the task evenly among the three threads. And each thread has to add up and report the answer to the main thread where the main thread waits for the 3 threads and computes the summation of all the three threads. Note: Assign names to the threads as well.