• public interface StackADT { public void push(T element); public T pop(); } and the following Java code fragment: StackADT s = new StackADT(); s.push("hello"); s.push("hi"); System.out.println(s.pop());

• ------------why The above code has compilation errors.----------------

• String s;

• String[] arr = new String[5]; try {

• s = arr[0];

0. for (int i = 0; i < s.length(); ++i) s = s + arr[i];

   } catch (ArrayIndexOutOfBoundsException e) {

   System.out.println("Invalid index");

   } catch (NullPointerException e) {System.out.println("Null pointer");} catch (Exception e) {System.out.println("Exception");

1. -------What is printed when the above code is executed? -------why null pointer-----