1. Programming with Arrays 2
This slide set was compiled from the Absolute Java textbook slides (Walter Savitch) and the professor’s own class materials.
CSS161: Fundamentals of Computing

2. Sorting an Array – Selection Sort
Key algorithm
for (int index = 0; index < count; index++)
Place the indexth smallest element in a[index] 8 6 11 17 3 15 5 19 28 12 3 6 11 17 8 15 5 19 28 12 3 5 11 17 8 15 6 19 28 12 3 5 6 17 8 15 11 19 28 12 3 5 6 8 17 15 11 19 28 12 3 5 6 8 11 15 17 19 28 12 3 5 6 8 12 12 17 19 28 15 3 5 6 8 12 11 15 19 28 17 3 5 6 8 12 11 15 17 28 19
CSS161: Fundamentals of Computing 3 5 6 8 12 11 15 17 19 28

3. First Swapping in Selection Sort
CSS161: Fundamentals of Computing

4. Second Swapping in Selection Sort
CSS161: Fundamentals of Computing

5. Code for Selection Sort (1 of 3)
public class SelectionSort {
/**
Precondition: numberUsed <= a.length;
The first numberUsed indexed variables have values.
Action: Sorts a so that a[0] <= a[1] <= ... <= a[numberUsed - 1]. */
public static void sort(double[] a, int numberUsed)
int index, indexOfNextSmallest;
for (index = 0; index < numberUsed - 1; index++)
{//Place the correct value in a[index]:
indexOfNextSmallest = indexOfSmallest(index, a, numberUsed);
interchange(index,indexOfNextSmallest, a);
//a[0] <= a[1] <=...<= a[index] and these are the smallest
//of the original array elements. The remaining positions
//contain the rest of the original array elements. }
CSS161: Fundamentals of Computing

6. Code Code for Selection Sort (2 of 3)
/**
Returns the index of the smallest value among
a[startIndex], a[startIndex+1], ... a[numberUsed - 1] */
private static int indexOfSmallest(int startIndex,
double[] a, int numberUsed) {
double min = a[startIndex];
int indexOfMin = startIndex;
int index;
for (index = startIndex + 1; index < numberUsed; index++)
if (a[index] < min)
min = a[index];
indexOfMin = index;
//min is smallest of a[startIndex] through a[index] }
return indexOfMin;
CSS161: Fundamentals of Computing

7. Code for Selection Sort (3 of 3)
/**
Precondition: i and j are legal indices for the array a.
Postcondition: Values of a[i] and a[j] have been interchanged. */
private static void interchange(int i, int j, double[] a) {
double temp;
temp = a[i];
a[i] = a[j];
a[j] = temp; //original value of a[i] }
CSS161: Fundamentals of Computing

8. CSS161: Fundamentals of Computing
Self-Test Exercises
Work on textbook p378’s exercises 20 ~ 21.
Trace Selection Sort with the following set of number:
int a[9] = {4, 7, 8, 5, 6, 0, 1, 2, 3};
CSS161: Fundamentals of Computing

9. CSS161: Fundamentals of Computing
Enumerated Types
Syntax
enum Type_Name {VALUE_1, VALUE_2 …, VALUE_N};
Example
enum WorkDay {MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY};
Variables
WorkDay meetingDay = null;
meetingDay = WorkDay.THURSDAY;
if ( meetingDay == WorkDay.MONDAY )
System.out.println( “A blue Monday” );
CSS161: Fundamentals of Computing

10. CSS161: Fundamentals of Computing
An Enumerated Type
CSS161: Fundamentals of Computing

11. Methods Included with Enumerated Type (1of 3)
CSS161: Fundamentals of Computing

12. Methods Included with Enumerated Type (2 of 3)
CSS161: Fundamentals of Computing

13. Methods Included with Enumerated Type (3 of 3)
CSS161: Fundamentals of Computing

14. CSS161: Fundamentals of Computing
The values( ) Method
CSS161: Fundamentals of Computing

15. CSS161: Fundamentals of Computing
The values( ) Method
CSS161: Fundamentals of Computing

16. Enumerated Type in a switch Statement (1 of 3)
CSS161: Fundamentals of Computing

17. Enumerated Type in a switch Statement (2 of 3)
CSS161: Fundamentals of Computing

18. Enumerated Type in a switch Statement (3 of 3)
CSS161: Fundamentals of Computing