1. Section 11.1
Introduction to
Data Structures

2. First Data Structure Definition
A data structure is a data type whose components are smaller data structures and/or simple data types.

3. Data Structure Starting Point
Any data type that can store more than one value is a data structure.

4. First Array Definition
An array is a data structure with one, or more, elements of the same type.
A 1-dimensional array is frequently called a vector.
A 2-dimensional array is frequently called a matrix.
The array is the first historical data structure which was introduced in the language FORTRAN.

5. Record Definition
A record is a data structure with one, or more, elements, called fields, of the same or different data types.
The language FORTRAN did NOT
have records which is why it
was NOT good for business.
COBOL (Common Business
Oriented Language) introduced
the record data structure.

6. A Note About Classes
A class is a record
that can also store methods.

7. File Definition
A file is an internal data structure - with an unspecified number of elements of the same type - assigned to an external file name.
The file data structure
allows transfer of data
between internal and
external storage.

8. Stack Definition
A stack is a data structure with elements of the same type.
Data elements of the stack data structure can only be accessed (stored or retrieved) at one end of the stack in a LIFO (Last In, First Out) manner.

9. Improved Data Structure Definition
A data structure is a data type whose components are smaller data structures and/or simple data types.
The storing and retrieval of the data elements is performed by accessing methods that characterize the data structure.

10. Section 11.2
Array
Definition

11. First Array Definition Again
An array is a data structure with one, or more, elements of the same type.
How exactly
is this different
from a stack?

12. Improved Array Definition
An array is a data structure with a fixed number of elements of the same type.
Every element of the array can be accessed directly.
Both a stack and an array
store elements of the same type,
but each accesses the data differently,
which makes them different data structures.

13. Array Example [16] Ingrid [17] Darlene [18] Gene [19] Sean [20]
Stephanie
[11]
Holly
[12]
Blake
[13]
Michelle
[14]
Remy
[15]
Haley
[06]
Diana
[07]
Jessica
[08]
David
[09]
Anthony
[10]
Alec
[01]
Isolde
[02]
John
[03]
Greg
[04]
Maria
[05]
Heidi

14. Section 11.3
1D Array
Declarations
and Access

15. // Java1101.java
// This program declares 10 different int variables.
// Each variable is assigned a value and each variable value is displayed.
// This approach is very inefficient for a large number of variables.   
public class Java1101 {
public static void main(String[] args)
int number0 = 100; int number1 = 101;
int number2 = 102; int number3 = 103;
int number4 = 104; int number5 = 105;
int number6 = 106; int number7 = 107;
int number8 = 108; int number9 = 109;
System.out.print(number0 + " ");
System.out.print(number1 + " ");
System.out.print(number2 + " ");
System.out.print(number3 + " ");
System.out.print(number4 + " ");
System.out.print(number5 + " ");
System.out.print(number6 + " ");
System.out.print(number7 + " ");
System.out.print(number8 + " ");
System.out.print(number9 + " ");
System.out.println(); }

16. // Java1102.java
// This program declares an array of 10 <int> elements.
// Each array element value is individually assigned and displayed.
// There does not appear any real benefit from the from program example.   
public class Java1102 {
public static void main(String[] args)
int list[]; // declares the array object identifier
list = new int[10]; // allocates memory for 10 array elements
list[0] = 100; list[1] = 101;
list[2] = 102; list[3] = 103;
list[4] = 104; list[5] = 105;
list[6] = 106; list[7] = 107;
list[8] = 108; list[9] = 109;
System.out.print(list[0] + " ");
System.out.print(list[1] + " ");
System.out.print(list[2] + " ");
System.out.print(list[3] + " ");
System.out.print(list[4] + " ");
System.out.print(list[5] + " ");
System.out.print(list[6] + " ");
System.out.print(list[7] + " ");
System.out.print(list[8] + " ");
System.out.print(list[9] + " ");
System.out.println(); }
Index
Value
100 1
101 2
102 3
103 4
104 5
105 6
106 7
107 8
108 9
109

17. Array Index Note
Java arrays indicate individual elements with an index inside two brackets, following the array identifier, like list[3]
The array index is always an integer and starts at 0.
In an array of N elements, the largest index is N-1.

18. // Java1103.java
// The previous program with separate statements for each array member
// assignment and display is now replaced with two loops. The loop counter,
// index, is used to specify each array element in an efficient manner.   
public class Java1103 {
public static void main(String[] args)
int list[];
list = new int[10];
for (int index = 0; index <=9; index++)
list[index] = index + 100;
System.out.print(list[index] + " ");
System.out.println(); }
Index
Value
100 1
101 2
102 3
103 4
104 5
105 6
106 7
107 8
108 9
109

19. Defining Static Arrays
int list[]; // declares the array list identifier
list = new int[10]; // allocates memory for 10 integers
char names[]; // declares the names array identifier
names = new char[25]; // allocates memory for 25 characters
double grades[]; // declares the grades array identifier
grades = new double[50]; // allocates memory for 50 doubles
In some old programming languages
that do not have a String data type,
an Array of characters is used instead.

20. Defining Static Arrays Preferred Method
int list[ ] = new int[10];
char names[ ] = new char[25];
double grades[ ] = new double[50];

21. This is similar to what you learned in Chapters 3 & 6.
This will work:
This is preferred: 3
int x;
x = 5;
int x = 5; 6
Bank tom;
tom = new Bank();
Bank tom = new Bank(); 11
int list[ ];
list = new int [10];
int list[ ] = new int[10];

22. // Java1104.java
// This program is the same list array and the same list values
// as the previous program. This time note that the array declaration
// is accomplished with a single statement.
public class Java1104 {
public static void main(String[] args)
int list[] = new int[10];
for (int index = 0; index <=9; index++)
list[index] = index + 100;
System.out.print(list[index] + " "); }
Index
Value
100 1
101 2
102 3
103 4
104 5
105 6
106 7
107 8
108 9
109

23. This is called an initializer list.
// Java1105.java
// This program demonstrates how to initialize array elements.
// The <new> operator is not necessary in this case.
public class Java1105 {
public static void main(String[] args)
int list[] = {100,101,102,103,104,105,106,107};
for (int k = 0; k <= 7; k++)
System.out.println("list[" + k + "] = " + list[k]);
System.out.println(); }
This is called an initializer list.
Note that the size of the array does not need to be specified.

24. // This program demonstrates how to initialize array elements.
// Java1105.java
// This program demonstrates how to initialize array elements.
// The <new> operator is not necessary in this case.
public class Java1105 {
public static void main(String[] args)
int list[] = {100,101,102,103,104,105,106,107};
for (int k = 0; k <= 7; k++)
System.out.println("list[" + k + "] = " + list[k]);
System.out.println(); }
list[0] = 100
list[1] = 101
list[2] = 102
list[3] = 103
list[4] = 104
list[5] = 105
list[6] = 106
list[7] = 107 1 2 3 4 5 6 7
100
101
102
103
104
105
106
107

25. list2 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
// Java1106.java
// This program demonstrates a character array and a string array.
// Both arrays use an initializer list.
public class Java1106 {
public static void main(String[] args)
char list1[] = {'A','B','C','D','E','F','G','H','I','J','K','L','M',
'N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
for (int k = 0; k < 26; k++)
System.out.print(list1[k]);
System.out.println("\n");
String list2[] = {"John","Greg","Maria","Heidi","Diana","David"};
for (int k = 0; k < 6; k++)
System.out.println(list2[k]);
System.out.println(); } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
ABCDEFGHIJKLMNOPQRSTUVWXYZ
John Greg Maria Heidi Diana David
list2 1 2 3 4 5
John
Greg
Maria
Heidi
Diana
David

26. Try This! Add one or more names to this list.
Will they show up in the output? Why?
// Java1106.java
// This program demonstrates a character array and a string array.
// Both arrays use an initializer list.
public class Java1106 {
public static void main(String[] args)
char list1[] = {'A','B','C','D','E','F','G','H','I','J','K','L','M',
'N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
for (int k = 0; k < 26; k++)
System.out.print(list1[k]);
System.out.println("\n");
String list2[] = {"John","Greg","Maria","Heidi","Diana","David"};
for (int k = 0; k < 6; k++)
System.out.println(list2[k]);
System.out.println(); }

27. Now Try This! Remove several names from this list.
Does the program still work? Why?
// Java1106.java
// This program demonstrates a character array and a string array.
// Both arrays use an initializer list.
public class Java1106 {
public static void main(String[] args)
char list1[] = {'A','B','C','D','E','F','G','H','I','J','K','L','M',
'N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
for (int k = 0; k < 26; k++)
System.out.print(list1[k]);
System.out.println("\n");
String list2[] = {"John","Greg","Maria","Heidi","Diana","David"};
for (int k = 0; k < 6; k++)
System.out.println(list2[k]);
System.out.println(); }

28. There are 4 array elements. names[0] = Joe names[1] = Tom
// Java1107.java
// This program introduces the length field to determine the
// number of elements in the array. Remove the comments from line 17
// to observe what happens when the length field is altered.
public class Java1107 {
public static void main(String[] args)
String names[ ] = {"Joe","Tom","Sue","Meg"};
int n = names.length; // data field access; not a method call
System.out.println("There are " + n + " array elements.");
for(int k = 0; k < n ; k++)
System.out.println("names[" + k + "] = " + names[k]);
// names.length = 10; }
There are 4 array elements.
names[0] = Joe
names[1] = Tom
names[2] = Sue
names[3] = Meg 1 2 3
Joe
Tom
Sue
Meg

29. Try This! Add one or more names to this list.
Will they show up in the output? Why?
Why is this different from program Java1106?
// Java1107.java
// This program introduces the length field to determine the
// number of elements in the array. Remove the comments from line 16
// to observe what happens when the length field is altered.
public class Java1107 {
public static void main(String[] args)
String names[ ] = { "Joe","Tom","Sue","Meg"};
int n = names.length; // data field access; not a method call
System.out.println("There are " + n + " array elements.");
for(int k = 0; k < n ; k++)
System.out.println("names[" + k + "] = " + names[k]);
// names.length = 10; }

30. Now Try This! Remove several names from this list.
Does the program still work? Why?
Why is this different from program Java1106?
// Java1107.java
// This program introduces the length field to determine the
// number of elements in the array. Remove the comments from line 16
// to observe what happens when the length field is altered.
public class Java1107 {
public static void main(String[] args)
String names[ ] = { "Joe","Tom","Sue","Meg"};
int n = names.length; // data field access; not a method call
System.out.println("There are " + n + " array elements.");
for(int k = 0; k < n ; k++)
System.out.println("names[" + k + "] = " + names[k]);
// names.length = 10; }

31. Try This Also!
Remove the comment symbol from the last program statement in this program.
Will the program still compile?
// Java1107.java
// This program introduces the length field to determine the
// number of elements in the array. Remove the comments from line 16
// to observe what happens when the length field is altered.
public class Java1107 {
public static void main(String[] args)
String names[ ] = { "Joe","Tom","Sue","Meg"};
int n = names.length; // data field access; not a method call
System.out.println("There are " + n + " array elements.");
for(int k = 0; k < n ; k++)
System.out.println("names[" + k + "] = " + names[k]);
// names.length = 10; }

32. NO! The length field is a final or constant attribute
// Java1107.java
// This program introduces the length field to determine the
// number of elements in the array. Remove the comments from line 16
// to observe what happens when the length field is altered.
public class Java1107 {
public static void main(String[] args)
String names[ ] = { "Joe","Tom","Sue","Meg"};
int n = names.length; // data field access; not a method call
System.out.println("There are " + n + " array elements.");
for(int k = 0; k < n ; k++)
System.out.println("names[" + k + "] = " + names[k]);
names.length = 10; }
NO!
The length field is a
final or constant attribute
just like the PI in Math.PI

33. Static Arrays vs. Dynamic Arrays
The size or length of a static array cannot
be changed.
This is why it is called a static array.
The size of a dynamic array can be changed.
You will learn about dynamic arrays in the next chapter.

34. Section 11.4
Random
Arrays

35. public static void main(String[] args) int list[] = new int[20];
// Java1108.java
// This program fills an <int> array with a random set of numbers.
public class Java1108 {
public static void main(String[] args)
int list[] = new int[20];
for (int k = 0; k < 20; k++)
double temp = Math.random() * 900;
int rand = (int) temp + 100;
list[k] = rand; }
System.out.println("list[" + k + "] = " + list[k]);
list[0] = 244
list[1] = 594
list[2] = 902
list[3] = 385
list[4] = 949
list[5] = 792
list[6] = 636
list[7] = 894
list[8] = 126
list[9] = 103
list[10] = 938
list[11] = 592
list[12] = 584
list[13] = 112
list[14] = 766
list[15] = 791
list[16] = 447
list[17] = 298
list[18] = 596
list[19] = 243 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
244
594
902
385
949
792
636
894
126
103
938
592
584
112
766
791
447
298
596
243

36. // Java1109.java
// This program will display 15 random sentences.
// With 7 different ranks, 7 different people, 7 different actions and 7 different locations,
// there are more than 2400 different sentences possible.
Random random = new Random();
String rank[ ] = {"Private","Corporal","Sargent","Lieutenant","Captain","Major","General"};
String person[ ] = {"Smith", "Gonzales", "Brown", "Jackson", "Powers", "Jones", "Nguyen"};
String action[ ] = {"drive the tank", "drive the jeep", "take the troops", "bring all supplies",
"escort the visitor", "prepare to relocate", "bring the Admiral"};
String location[ ] = {"over the next hill", "to the top of the mountain", "outside the barracks",
"30 miles into the dessert", "to the middle of the forest",
"to my present location", "to anywhere but here"};
for (int j = 1; j <= 15; j++) {
int randomRank = random.nextInt(rank.length);
int randomPerson = random.nextInt(person.length);
int randomAction = random.nextInt(action.length);
int randomLocation = random.nextInt(location.length);
String sentence = rank[randomRank] + " " + person[randomPerson] + " " +
action[randomAction] + " " + location[randomLocation] + ".";
System.out.println("\n" + sentence); }

37. Sargent Brown, bring all supplies outside the barracks.
Major Brown, drive the tank to anywhere but here.
General Smith, prepare to relocate to the middle of the forest.
Corporal Jones, bring the Admiral over the next hill.
General Jackson, take the troops outside the barracks.
Captain Brown, escort the visitor to my present location.
Corporal Powers, drive the tank to my present location.
Private Smith, drive the jeep to my present location.
Captain Jackson, escort the visitor to anywhere but here.
Corporal Smith, bring the Admiral over the next hill.
Corporal Smith, drive the jeep to anywhere but here.
Corporal Gonzales, prepare to relocate outside the barracks.
Major Gonzales, escort the visitor to the top of the mountain.
Major Smith, escort the visitor to the top of the mountain.
Lieutenant Gonzales, escort the visitor over the next hill.

38. Accessing Array Elements
Section 11.5
Accessing Array Elements
with the for..each
Loop Structure

39. // Java1110.java
// This program introduces the Java Version 5.0 enhanced <for..each> loop
// with an <int> array.
public class Java1110 {
public static void main(String[] args)
int list[] = {11,22,33,44,55,66,77,88,99};
for (int k = 0; k < 9; k++) // Old <for> loop syntax
System.out.print(list[k] + " ");
System.out.println("\n\n");
for (int item: list) // New <for> loop syntax
System.out.print(item + " "); }

40. Tom Sue Joe Jan Bob Lee Ann Meg
// Java1111.java
// This program uses the Java Version 5.0 <for..each> loop with a <String> array.
public class Java1111 {
public static void main(String[] args)
String names[] = {"Tom","Sue","Joe","Jan","Bob","Lee","Ann","Meg"};
for (int k = 0; k < 8; k++) // Old <for> loop syntax
System.out.print(names[k] + " ");
System.out.println("\n\n");
for (String name: names) // New <for> loop syntax
System.out.print(name + " "); }
Tom Sue Joe Jan Bob Lee Ann Meg

41. // Java1112.java
// This program demonstrates a very generalized <for..each> loop usage
// with the <Object> class.
public class Java1112 {
public static void main(String[] args)
System.out.println("Java1112\n");
String names[] = {"Tom","Sue","Joe","Jan","Bob","Lee","Ann","Meg"};
for (int k = 0; k < 8; k++)
System.out.print(names[k] + " ");
System.out.println("\n\n");
for (Object obj: names)
System.out.print(obj + " "); }

42. Enhancing the for Loop
The enhanced for loop is called the for .. each loop.
The new loop structure does not replace the older for loop, because it is not possible to access specific array elements.
int numbers[ ] = {1,2,3,4,5,6,7,8,9};
for (int number: numbers)
System.out.print(number + " ");

43. Section 11.6
Shallow & Deep
Values of Arrays

44. // Java1112.java
// This program shows that actual parameters are not
// altered by a call to the <swap> method.
public class Java1112 {
public static void main(String[] args)
int p = 10;
int q = 20;
System.out.println(p + " " + q);
swap(p,q); }
public static void swap (int x, int y)
int temp = 0;
System.out.println(x + " " + y);
temp = x;
x = y;
y = temp;
10 20
20 10

46. // Java1113.java
// In this program it appears that a call to the <swap>
// can alter values in the calling method.
public class Java1113 {
public static void main(String[] args)
int[ ] list = {111,222,333,444,555,666,777,888,9999};
System.out.println(list[3] + " " + list[4]);
swap(list,3,4); }
public static void swap(int[ ] x, int p, int q)
int temp = x[p];
x[p] = x[q];
x[q] = temp;

49. Section 11.7
Review of the
Card Class

50. // Card01.java
// This <Card> class is the version,
// which was introduced in Chapter IX.
// ///////////////////////////////////////////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class Card01 {
private String suit;
private String rank;
private int value;
public Card01(String s, String r, int v)
suit = s;
rank = r;
value = v; }
public String getSuit() { return suit; }
public String getRank() { return rank; }
public int getValue() { return value; }
public void setSuit(String s) { suit = s; }
public void setRank(String r) { rank = r; }
public void setValue(int v) { value = v; }

51. // Card02.java
// The <Card02> class re-defines the <toString> method,
// which is used to display the <Card02> attributes.
// ///////////////////////////////////////////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class Card02 {
private String suit;
private String rank;
private int value;
public Card01(String s, String r, int v)
suit = s;
rank = r;
value = v; }
public String getSuit() { return suit; }
public String getRank() { return rank; }
public int getValue() { return value; }
public void setSuit(String s) { suit = s; }
public void setRank(String r) { rank = r; }
public void setValue(int v) { value = v; }
public String toString() {
return "[" + suit + ", " + rank + ", " + value + "]"; }

52. Suit: Spades Rank: Ace Value: 11 [Hearts, Seven, 7]
// CardTester02.java
// This program tests the <Card02> class.
// /////////////////////////////////////////////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class CardTester02 {
public static void main(String[] args)
Card02 card = new Card02("Spades","Ace",11);
System.out.println("Suit: " + card.getSuit());
System.out.println("Rank: " + card.getRank());
System.out.println("Value: " + card.getValue());
System.out.println();
card.setSuit("Hearts");
card.setRank("Seven");
card.setValue(7);
System.out.println(card); }
Suit: Spades
Rank: Ace
Value: 11
[Hearts, Seven, 7]

53. // Card03.java
// The <Card03> class adds the <matches> method.
// This class now is identical to the <Card> class of the "Elevens" lab.
// ///////////////////////////////////////////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class Card03 {
private String suit;
private String rank;
private int value;
public Card03(String s, String r, int v)
suit = s;
rank = r;
value = v; }
public String suit() { return suit; }
public String rank() { return rank; }
public int value() { return value; }
public boolean matches(Card otherCard) { return otherCard.getSuit().equals(this.suit) && otherCard.getRank().equals(this.rank) && otherCard.getValue() == this.value; }
public String toString() { return "[" + suit + ", " + rank + ", " + value + "]"; }

54. [Spades, Ace, 11] [Clubs, Seven, 7] false true // CardTester03.java
// This program tests the <Card03> class.
// //////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class CardTester03 {
public static void main(String[] args)
Card03 card1 = new Card03("Spades","Ace",11);
Card03 card2 = new Card03("Seven","Clubs",7);
Card03 card3 = new Card03("Spades","Ace",11);
System.out.println(card1);
System.out.println(card2);
System.out.println(card3);
System.out.println();
System.out.println(card1.matches(card2));
System.out.println(card1.matches(card3));
System.out.println(card2.matches(card3)); }
[Spades, Ace, 11]
[Clubs, Seven, 7]
false
true

55. Section 11.8
Arrays as
Class Attributes

56. // Deck01.java
// The first stage of the <Deck> is very basic.
// It shows how the <Card> class is used to create a
// <cards> array as a data structure attribute of the <Deck> class.
// ////////////////////////////////////////////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class Deck01 {
private Card[] cards;
private int size;
public Deck01()
cards = new Card[52];
size = 0; }
public int size() { return size; }
public boolean isEmpty() { return size == 0; }

57. Deck01@1db9742 true // DeckTester01.java
// This program tests the <Deck01> class.
// ///////////////////////////////////////////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class DeckTester01 {
public static void main(String[] args)
Deck01 deck = new Deck01();
System.out.println(deck);
System.out.println(deck.size());
System.out.println(deck.isEmpty()); }
true

58. // Deck02.java
// Methods <add> and <display> are added to the <Deck02> class.
// Objects of the <Card> class can now be stored in the <cards> array.
// ///////////////////////////////////////////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class Deck02 {
// only new methods shown
public void add(String suit, String rank, int value)
Card temp = new Card(suit,rank,value);
cards[size] = temp;
size++; }
public void display()
for (int k = 0; k < size; k++)
System.out.println(cards[k]);
System.out.println();

59. deck.add("Clubs","Three",3); deck.add("Diamonds","Four",4);
// DeckTester02.java
// This program tests the <Deck02> class.
// //////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class DeckTester02 {
public static void main(String[] args)
Deck02 deck = new Deck02();
deck.add("Clubs","Three",3);
deck.add("Diamonds","Four",4);
deck.add("Hearts","Five",5);
deck.add("Spades","Six",6);
deck.display();
System.out.println(deck.size());
System.out.println(deck.isEmpty()); }
[Clubs, Three, 3]
[Diamonds, Four, 4]
[Hearts, Five, 5]
[Spades, Six, 6] 4
false

60. // Deck02.java
// Methods <add> and <display> are added to the <Deck02> class.
// Objects of the <Card> class can now be stored in the <cards> array.
// //////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class Deck02 {
// only new methods shown
public void add(String suit, String rank, int value)
Card temp = new Card(suit,rank,value);
cards[size] = temp;
size++; }
public void display()
for (Card card: cards) System.out.println(card);
System.out.println();
Try This!
Change the display method so that it uses the for..each loop. Recompile and execute Decktester02.java.

61. Important Note:
You just saw an example where a fundamental question was raised.
Does the new for..each loop provide
the same output as the traditional index for loop?
Both loops do display the array elements, but the indexed loop can be easily controlled to only include those elements that reference a deeper value.
It is precisely in the asking of the what..if questions, followed by some experimenting that students learn the most about programming.

62. // Deck03.java
// The <display> method is now replaced by the <toString> method.
// ////////////////////////////////////////////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class Deck03 {
// only new methods shown
public String toString()
String temp = "";
for (int k = 0; k < size; k++)
temp = temp + cards[k].toString() + "\n";
return temp; }

63. System.out.println(deck); [Clubs, Three, 3] [Diamonds, Four, 4]
// DeckTester03.java
// This program tests the <Deck03> class.
// //////////////////////////////////////////////////////////
// This program is designed to explain the "Elevens" lab created
// by Michael Clancy, Robert Glen Martin and Judith Hromcik.
// Divided into stages and altered August 2014 by Leon Schram.
public class DeckTester03 {
public static void main(String[] args)
Deck03 deck = new Deck03();
deck.add("Clubs","Three",3);
deck.add("Diamonds","Four",4);
deck.add("Hearts","Five",5);
deck.add("Spades","Six",6);
System.out.println(deck);
System.out.println(deck.size());
System.out.println(deck.isEmpty()); }
[Clubs, Three, 3]
[Diamonds, Four, 4]
[Hearts, Five, 5]
[Spades, Six, 6] 4
false