Here the code for get three digit value 'n' and calculate r=2^n+1 then find that value 'r' is a prie or not, here i like store the integer value 'r' without exponential function and big Integer, please make a great help to me.
thanks in advance..

import java.*;
import java.math.*;

public class primenumber extends power{

public static void main(String a[])throws IOException {
//get input
power ob=new power();
DataInputStream dis=new DataInputStream(;
System.out.println(" Enter three digit number n:");
String nu=dis.readLine();
int n=Integer.parseInt(nu);
long nvalue=ob.powerr(n);

//find prime
long r;
int primevalue=0,i,j=0;
long factors[]=new long[100];

//System.out.println("not prime");
}//inner if
}//outer if
}//for ends
System.out.println("Given number is"+n+"");
System.out.println("Prime calculation for"+nvalue+"");
System.out.println("power value is"+nvalue+"");

System.out.println("The number "+nvalue+" is prime");
System.out.println("The number "+nvalue+" is not a prime");
for(int k=0;k<=j-1;k++)
System.out.print("," +factors[k]);

}//main end here
}//class end here

class power {
//find power
final int two=2;
long powvalue=1 , i;
long powerr(int x){
int n=x;
return powvalue;

try what? what are you stuck with? what is it supposed to do and what is it (not) doing?

could you be a bit more specific about these things?

Sample output:1
Enter three digit number n:
Given number is13
Prime calculation for16384
power value is16384
The number 16384 is not a prime
BUILD SUCCESSFUL (total time: 9 seconds)

Sample output:2
Enter three digit number n:
Given number is26
Prime calculation for134217728
power value is134217728
The number 134217728 is not a prime
BUILD SUCCESSFUL (total time: 9 seconds)

if you give 31 (or) any big value as a input, system could not give output.Because prime calculation number "nvalue" will be a very big integer.

i gave 31 as an input and i got bug form system, please go through ..
Sample output:3
Enter three digit number n:
Exception in thread "main" java.lang.ArithmeticException: / by zero
at primenumber.main(
Java Result: 1
BUILD SUCCESSFUL (total time: 4 minutes 2 seconds)

if you are asked: enter a three-digit number, why do you only test with two-digit numbers? that Exception says that on line 40 of the code in your main class, you are dividing something by zero, which causes your exception

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