Required: Variable - Found: Value (Java)

Question

Error: "Required: Variable - Found: Value"
How can I correct it?

public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);

String e = sc.next();
int l = e.length();
for(int i = 0; i < l; i++)
{
if(e.charAt(i) != '(' || e.charAt(i) != ')')
>>>> e.charAt(i) = ''; <<<< (Error!!!)
}
char[] exp = e.toCharArray();
}