Thread: Trouble when I try to do without using a compound assignment operator

I'm encountering some unexpected error messages when I try to do without a compound assignment operator. Here's my code:

package samsExperiments;
 
public class SamsArrays {	
 
	public int getAverage(int[] arr) {
		int sum = 0;
		for(int x : arr) {
			sum + x = sum;
			(sum + x) = sum;
			sum += x;
		}
	}	
}

Line 8 error: "Syntax error on token "+", invalid AssignmentOperator"

Line 9 error: "The left-hand side of an assignment must be a variable"

What's wrong? Why does it see an addition symbol as an assignment operator, when the = sign is clearly on the right-hand side of the x variable? And since sum and x are obviously both variables, why is it saying they're not?