text: Primality Test | Set 5 ( Using Lucas | Java program to check for primality using Lucas - Lehmer series . ; Function to check whether ( 2 ^ p - 1 ) is prime or not . ; generate the number ; First number of the series ; Generate the rest ( p - 2 ) terms of the series . ; now if the ( p - 1 ) th term is 0 return true else false . ; Driver Program ; Check whether 2 ^ p - 1 is prime or not .
code: class GFG { static boolean isPrime ( int p ) { double checkNumber = Math . pow ( 2 , p ) - 1 ; double nextval = 4 % checkNumber ; for ( int i = 1 ; i < p - 1 ; i ++ ) nextval = ( nextval * nextval - 2 ) % checkNumber ; return ( nextval == 0 ) ; } public static void main ( String [ ] args ) { int p = 7 ; double checkNumber = Math . pow ( 2 , p ) - 1 ; if ( isPrime ( p ) ) System . out . println ( ( int ) checkNumber + " ▁ is ▁ Prime . " ) ; else System . out . println ( ( int ) checkNumber + " ▁ is ▁ not ▁ Prime . " ) ; } }