Write Java Encryption class to Encrypt API key

Write Encryption and decryption class in java to secure API key, following things needed in class: 1) Encrypt message using provided public key(RSA4096) 2) Decrypt message using provided private key(RSA4096)([login to view URL]) 3) Public/private key is generated from openssl 4) Create a key holder which can store private key safely *Note: Need this encryption class to encrypt Real time transaction Bank API access key. So need extreme security