Update StreamCipher.java

Many Time Pad 

Let us see what goes wrong when a stream cipher key is used more than once. Below are eleven hex-encoded ciphertexts that are the result of encrypting eleven plaintexts with a stream cipher, all with the same stream cipher key. Your goal is to decrypt the last ciphertext, and submit the secret message within it as solution. 

Hint: XOR the ciphertexts together, and consider what happens when a space is XORed with a character in [a-zA-Z]