How to explain whether Exception will catch RuntimeException?

The premise of the question is flawed, because catching Exception does catch RuntimeException. Demo code:

public class Test {
    public static void main(String[] args) {
        try {
            throw new RuntimeException("Bang");
        } catch (Exception e) {
            System.out.println("I caught: " + e);
        }
    }
}

Output:

I caught: java.lang.RuntimeException: Bang

Your loop will have problems if:

• callbacks is null
• anything modifies callbacks while the loop is executing (if it were a collection rather than an array)

Perhaps that’s what you’re seeing?