Java- Object-Oriented and Concurrent Programming

1. (10 pts) What are the diagrams defined in the UML Standard. Give a one or two sentence description of each one.

2. (10 pts) Given the following code, how should the toString methods in the classes H2ClassA and H2ClassB be written to give the indicated output and take advantage of the natural toString method in H2ClassB?

1  import java.util.ArrayList;
2
3  publicclass H2ClassA {
4    ArrayList <H2ClassB> list = new ArrayList <H2ClassB> ();
5
6    publicstaticvoid main (String args []) {
7      H2ClassA y = new H2ClassA ();
8      int [] v = {4, 3, 7, 5, 99, 3};
9      for (int m: v)
10       y.list.add (new H2ClassB (m));
11     System.out.println (y);
12   } // end main
13
14 } // end class H2ClassA
15
16 class H2ClassB {
17   int x;
18   H2ClassB (int a) { x = a;}
19 } // end H2ClassB

OUTPUT:

4 3 7 5 99 3

3. (10 pts) How can the following code be corrected? Give at least two good answers.

1 publicclass H2ClassC {
2   H2ClassC (int a) {}
3 } // end class H2ClassC
4
5 class H2ClassD extends H2ClassC{
6 } // end class H2ClassD

4. (10 pts) Why does the following code give a compiler error? How should it be fixed?

 

1  publicclass H2ClassE {
2    int x, y, z;
3
4    H2ClassE (int a) {
5      x = a;
6      this (5, 12);
7    }
8
9    H2ClassE (int b, int c) {
10     y = b;
11     z = c;
12   }
13 } // end class H2ClassE

5. (10 pts) What is wrong with the following declaration? How should it be fixed?

public static final int myNumber = 17.36;

6. (10 pts) What is wrong with the following code? How should it be fixed?

1 publicclass H2ClassG {
2   finalint x;
3
4   H2ClassG () {}
5   H2ClassG (int a) {x = a;}
6 } // end class H2ClassG

7. (10 pts) What is wrong with the following code? How should it be fixed?

1 publicclass H2ClassH {
2   finalint x;
3
4   int H2ClassH () {
5     if (x == 7) return 1;
6     return 2;
7   } // end
8 } // end class H2ClassH

8. (10 pts) What is wrong with the following code? x should be given a value of 24. What are two ways this can be legally accomplished?

1 publicclass H2ClassI {
2   finalint x;
3
4   publicstaticvoid main (String args []) {
5     H2ClassI h = new H2ClassI ();
6     h.x = 24;
7   } // end main
8 } // end class H2ClassI

9. (10 pts) What is wrong with the following code? Give two effective ways to fix it.

1  import javax.swing.*;
2  import java.awt.event.*;
3
4  publicclass H2ClassJ extends JFrame {
5    publicstaticfinallong serialVersionUID = 22;
6
7    public H2ClassJ () {
8      addMouseListener (new MouseListener () {
9        publicvoid mouseClicked (MouseEvent e) {}
10     });
11   } // end constructor
12
13 } // end class H2ClassJ

10. (10 pts) Why does the following code give a compiler warning? (Use javac -Xlint) How should it be fixed?

1 import javax.swing.*;
2
3 publicclass H2ClassK {
4   String [] sa = {"a", "b", "c"};
5   JComboBox jcbA = new JComboBox (sa);
6 } // end class H2ClassK