Could someone explain what is wrong with this java code?

Question

for (i = 0; i < 10; i++) {
    int sum;

    sum = sum+i;
}

System.out.println("Sum is " + sum);

I'm trying to figure out what is wrong with this piece of code that is supposed to run in java. In VSCode im getting a lot of errors when trying to compile and run it, but I can't seem to understand what is causing the errors.

Answer 1

sum is defined inside the loop, it's only available in that scope.

And i variable is not declared, it can be declared just in the loop.

This is a way to fix it:

int sum = 0;

for (int i = 0; i < 10; i++) {
    sum = sum + i; // or sum += i;
}

System.out.println("Sum is " + sum);

Answer 2

sum is declared inside for loop. It's scope end inside the loop and you are trying to access it outside the for loop and hence the compiler will throw error.