THINKING IN OBJECTS - Introduction to Java Programming - page 388

9 }
10
11

/** Construct a stack with the specified maximum capacity */

public StackOfIntegers( int capacity)

12 {

13 elements = new int [capacity];
14 }
15
16 /** Push a new integer to the top of the stack */
17 public void push( int value) {
18 if (size >= elements.length) {
19 int [] temp = new int [elements.length * 2 ];
20 System.arraycopy(elements, 0 , temp, 0 , elements.length);
21 elements = temp;
22 }
23
24 elements[size++] = value;
25 }
26
27

double the capacity

add to stack

/** Return and remove the top element from the stack */

28 public int pop() {

29 return elements[——size];

30 }
31
32 /** Return the top element from the stack */

33 public int peek() {

34 return elements[size - 1 ];

35 }
36
37

/** Test whether the stack is empty */

38 public boolean empty() {

39 return size == 0 ;

40 }
41
42 /** Return the number of elements in the stack */

43 public int getSize() {

44 return size;

45 }
46 }

10.10 Case Study: Designing the GuessDate Class
You can define utility classes that contain static methods and static data.

Key
Point

Listing 3.3, GuessBirthday.java, and Listing 7.6, GuessBirthdayUsingArray.java, presented
two programs for guessing birthdays. Both programs use the same data developed with the
procedural paradigm. The majority of the code in these two programs is to define the five sets
of data. You cannot reuse the code in these two programs, because the code is in the main
method. To make the code reusable, design a class to encapsulate the data, as defined in
Figure 10.13.
Note that getValue is defined as a static method because it is not dependent on a specific
object of the GuessDate class. The GuessDate class encapsulates dates as a private mem-
ber. The user of this class doesn't need to know how dates is implemented or even that the
dates field exists in the class. All that the user needs to know is how to use this method to
access dates. Suppose this class is available. As shown in Section 3.4, there are five sets of
dates. Invoking getValue(setNo, row, column) returns the date at the specified row and
column in the given set. For example, getValue(1, 0, 0) returns 2 .