为什么这个程序老提示有错
public class HelloWorld{
public static void main(String[] args) {
int one = 10 ;
int two = 20 ;
int three = 0 ;
three=one+two;
system.out.println("three =one +two ==>"+three);
three+=one;
system.out.println("three += one ==>"+three);
three-=one;
system.out.println("three -= one ==>"+three);
three*=one;
system.out.println("three *= one ==>"+three);
three/=one;
system.out.println("three /= one ==>"+three);
three%=one;
system.out.println("three %= one ==>"+three);
}
}