can a defined variable be defined again？

Question

int num2 = 4;
int num3 = ++num2;
int num3 = --num2;

why it tells me" variable num3 is already defined in method main(String[])"？

Answer 1

You cannot redefine or declare another variable with the same identifier or name within the same scope. However, you can *reassign* it with a new value by removing the data type in front. 😉

P/S: Updated scoping and credits go to @Rrestoring faith

Answer 2

You can have two variables of the same name if one is global and the other is local. Though, that isnt re-defining a variable. Since the compiler can determine which one you are referring to (local variables have higher priority).