Your if condition is not correct !
Your code should be :
public static void main(String [] args){
BigInteger i = new BigInteger("2");
double sqroot, cuberoot, fifthroot;
while(true) {
sqroot = Math.sqrt(i.floatValue());
cuberoot = Math.cbrt(i.floatValue());
fifthroot = Math.pow(i.floatValue(),1/5.0d);
System.out.print("i = "+i);
if(Math.floor(sqroot)==sqroot && Math.floor(cuberoot)==cuberoot && Math.floor(fifthroot)==fifthroot){
break;
}
i= i.add(new BigInteger("1"));
}
System.out.println(i);
}
1
solved Find the smallest number have 3 integer roots?