The most efficient way to crack your password is using the tool I released together with hashcat (a password cracker software):
https://github.com/floyd-fuh/JKS-private-key-cracker-hashcat
If you have a powerful graphic card (GPU), the cracking will be much faster. Otherwise hashcat will use your CPU.
It boils down to the following two commands:
java -jar JksPrivkPrepare.jar your_JKS_file.jks > hash.txt
./hashcat -m 15500 -a 3 hash.txt
The reason why this is much more efficient is that it will crack the private key password directly rather than the key store password. It uses an algorithm that no other password cracker has used before. Most password crackers are not very efficient (as they calculate the entire key store file into the SHA1 calculation) and in the worst case might even crack the key store password (which might not be the private key password that can be used for decryption of the key). If you need more details you can read the POC||GTFO journal article I wrote, which can be found here or on various other free mirrors: POC||GTFO journal - 15:12 Nail in the Java Key Store Coffin
For example if you have a NVidia 1080 graphic card you can try all alphanumeric passwords of length 8 in roughly 8 hours.