Java: Create a multithreaded program that reads all text files in a directory given by the user and creates a single output text file that counts the frequency of words found in all text files, combined. Ignore punctuation and symbols. Only words should be counted, and the program should automatically process ALL words in all input text files in the directory

example: suppose in a /textfiles directory, there exists:

input1.txt : "hello world"

input2.txt : "hello everyone"

input3.txt: "This is world for everyone"

input4.txt: "We are the world"

----------------------------------------------------------------------

Then either in the same directory or in a different directory, an output.txt file must contain:

hello: 2

world: 3

everyone: 2

is: 1

for: 1

this: 1

are: 1