As @Lester said, AES-128 is a strong cipher and easy to use.
What is not easy to use is to protect the key used to encipher the data before you serialize it. This may be a serious challenge to your design. If you store the key as a
string in the class/source, then someone can decompile the .class file and get the sting constant. Once they get the constant key, they can trivially decipher the data from the disk.
Depending on your threat model, you may be tempted to encode the key with something, but that is always essentially SBO, security by obscurity. And again, a decompile will show exectly what you are doing, and be obvious to the attacker.