Objects and classes - Data Structures and Problem Solving Using Java - page 102

figure 3.18
Code for
Exercise 3.13

1 class Person
2 {
3 public static final int NO_SSN = -1;
4
5 private int SSN = 0;
6 String name = null;
7 }
8
9 class TestPerson
10 {
11 private Person p = new Person( );
12
13 public static void main( String [ ] args )
14 {
15 Person q = new Person( );
16
17 System.out.println( p ); // illegal
18 System.out.println( q ); // legal
19
20 System.out.println( q.NO_SSN ); // ?
21 System.out.println( q.SSN ); // ?
22 System.out.println( q.name ); // ?
23 System.out.println( Person.NO_SSN ); // ?
24 System.out.println( Person.SSN ); // ?
25 }
26 }

Is the following import directive, which attempts to import virtually
the entire Java library, legal?

3.16

import java.*.*;

Suppose the code in Figures 3.3 ( TestIntCell ) and 3.4 ( IntCell ) are
both compiled. Then, the IntCell class in Figure 3.4 is modified by
adding a one-parameter constructor (thus removing the default zero-
parameter constructor). Of course if TestIntCell is recompiled, there
will be a compilation error. But if TestIntCell is not recompiled, and
IntCell is recompiled by itself, there is no error. What happens when
TestIntCell is then run?

3.17

IN PRACTICE
3.18

A combination lock has the following basic properties: the combina-
tion (a sequence of three numbers) is hidden; the lock can be opened
by providing the combination; and the combination can be changed,
but only by someone who knows the current combination. Design a