variable a might not have been initialized

if ((12000 <= a )&&(a < 12321)){

^

what is this mean?

im learning about loops at this point.Code:`public class tt{`

public static void main(String[]args){

int n = 1;

double a;

while ( n < 999)

a = Math.pow(n, 2);

if ((12000 < a )&&(a < 12321)){

System.out.println("The smallest n such that n^2 > 12,000 is " + n);

}

n++;

}

}