Q:

Difference between BigInteger.probablePrime() and other primality algorithms in java

I am implementing an RSA encryption program using Java.  Right now I am using   BigInteger.probablePrime(1024, rnd) to get prime numbers.   Here rnd is a random number generated by Random rnd = new Random() .  
I need to test various speeds of encryption. 
My questions are:

what algorithm does the BigInteger.probablePrime(1024, rnd) use?  
what is the difference between the algorithm above and other algorithms:  like Rabin-Miller, Fermats, Lucas-Lehmer?  

Thank you. 

A:

BigInteger's probable prime methods use both the Miller-Rabin and Lucas-Lehmer algorithms to test primality. 
See the internal method BigInteger.primeToCertainty.