CS122/504 QUIZ 1

                                   Prof. Lixin Tao

                                  February 23, 2006


1)  Questions 1 through 4 are based on the following definitions:

      -----------------Comparable.java-------------------
      package p1;
      public interface Comparable { int  compare(Object o); }
      -----------------A.java----------------------------
      package p1;
      public class A {
        protected int a;
        public void fa1() { ... }
        protected  void fa2() { ... }
        void  fa3() { ... }
      }
      -----------------B.java----------------------------
      package p1;
      public class B extends A {
        private int b;
        private void fb1() { ... }
        protected void fb2() { ... }
        public void fb3() { ... }
        public static void main(String[] args) {
          B b1 = new B();
          A b2 = b1;
          ......
        }
      }
      -----------------C.java----------------------------
      package p2;
      public class C extends p1.B implements p1.Comparable {
        public int compare(Object o) { ... }
        private void fc() { ... }
        public static void main(String[] args) {
          C c1 = new C();
          p1.Comparable c2 = c1;
          ......
        }
      }
      -----------------D.java---------------------------
      package p2;
      
      public class D {
        public static void main(String[] args) {
      	  C d = new C();
      	  ......
        }
      }

      From reference variable b1, which of the following data fields and methods can be accessed? (multiple answers) [10%]

      1)  a *
      2)  fa1() *
      3)  fa2() *
      4)  fa3() *
      5)  b *
      6)  fb1() *
      7)  fb2() *
      8)  fb3() *
      9)  fc()
     10)  compare(Object o)

2) Based on the same source code in question 1, from reference variable b2,  which of the following data fields and methods can be accessed? (multiple answers) [10%]


      1)  a *
      2)  fa1() *
      3)  fa2() *
      4)  fa3() *
      5)  b
      6)  fb1()
      7)  fb2()
      8)  fb3()
      9)  fc()
     10)  compare(Object o)

3) Based on the same source code in question 1, from reference variable c1,  which of the following data fields and methods can be accessed? (multiple answers) [10%]


      1)  a *
      2)  fa1() *
      3)  fa2() *
      4)  fa3()
      5)  b
      6)  fb1()
      7)  fb2() *
      8)  fb3() *
      9)  fc() *
     10)  compare(Object o) *

4) Based on the same source code in question 1, from reference variable c2,  which of the following data fields and methods can be accessed? (multiple answers) [10%]


      1)  a
      2)  fa1()
      3)  fa2()
      4)  fa3()
      5)  b
      6)  fb1()
      7)  fb2()
      8)  fb3()
      9)  fc()
     10)  compare(Object o) *

5) Based on the same source code in question 1, from reference variable d,  which of the following data fields and methods can be accessed? (multiple answers) [10%]


      1)  a 
      2)  fa1() *
      3)  fa2()
      4)  fa3()
      5)  b
      6)  fb1()
      7)  fb2()
      8)  fb3() *
      9)  fc()
     10)  compare(Object o) *

6) What do we mean that class A implements interface IF? (multiple answers) [10%]

      1) Class A will implement a graphic user interface based on IF.
      2) Class A promises to implement all methods in IF before it can be concrete. *
      3) An object of type A can save its reference in a reference variable of type IF. *
      4) From a reference variable of type IF, we can access all public methods defined for the object whose reference the variable is holding.

7) Write a class Stack of integers with array of integers, and let class Stack implement interface Iterator. 

        public interface Iterator {
          Iterator iterator();       // return an Iterator object for a data structure
          boolean hasNext();         // whether there are more unread integers in the iterator
          int next();                // return the next integer in the iterator
        }
[40%]