Java GuardedString - Is the random key used for encryption is stored inside Java Heap memory? If not, then where the key is persisted?

Oracle's org.identityconnectors.common.security.GuardedString

The raw data to be converted to GuardedString needs an encryption key that is randomly generated by EncryptorImpl.class.

I wondering where the randomly generated key is persisted(to be used for decryption)? If it is stored in Heap then it is vulnerable to attackers as they can get the key from the heap dump.