Else without if

you have an else statement after a for loop

for(int i=3;i*i<=n;i+=2)
{
    if(n%1==0)
    {
        System.out.println("Your number isn't prime.");
    }
}
else
{
    System.out.println("Your number is prime!");
}

you probably have to make a Boolean variable to do this one. there are various ways to do it, but here’s one that I would probably use

boolean isPrime = true;
for(int i=3;i*i<=n;i+=2)
{
    if(n%1==0)
    {
        isPrime = false;
    }
}
if(isPrime)
{
    System.out.println("Your number is prime!");
}
else
{
    System.out.println("Your number isn't prime.");
}