1. What If?
Write a program that prompts for the names and locations of 1000 employees. Store the information in the program for later use.

2. Program for Previous String empName1, empName2, empName3,…
String empLocation1, empLocation2, …
System.out.print( “Enter employee name 1:”);
empName1 = scan.next();
System.out.print(“Enter employee name 2:”);
empName2 = scan.next(); …
//Can we use a loop?

3. Arrays Syntax: type variableName[] = new type [size];
Memory Is Set Aside for size Items of type
Each Variable Location in Array Is Accessed by Offsetting into the Array with an Integer Expression
Legitimate Offsets Are 0 to size-1

4. Array Example char [] lastname = new char[100]; lastname[0] = ‘H’;
lastname[1] = ‘a’;
lastname[2] = ‘\0’;
System.out.println( lastname[0]);

5. Array Example int [] values = new int[15]; values[0] = 150;
System.out.println( values[0]);
values[3] = values[0] + 6;

6. Array Example final int ARRAY_SIZE = 100; int offset;
int [] numArray = new int [ARRAY_SIZE];
for(offset = 0; offset < ARRAY_SIZE; offset++) {
numArray[offset] = 0; }
for(offset = 0; offset < numArray.length; offset++)
numArray[offset] = offset;

7. Array Example final int ARRAY_SIZE = 10; int offset, sum = 0, average;
int [] numArray = new int[ARRAY_SIZE];
for(offset = 0; offset < ARRAY_SIZE; offset++) {
System.out.print( “Enter Score ” + offset + “ : “);
numArray[offset] = scan.nextInt(); }
sum = sum + numArray[offset];
average = sum / ARRAY_SIZE;

8. Arrays of Objects // The following does NOT create memory for
// objects, it only makes a blueprint array
Employee [] employees = new Employee [MAXEMP];
// Must create memory and call constructor for
// each single member of aray of objects
for (i = 0; i < MAXEMP; i++)
employees[i] = new Employee();

9. Passing Arrays to Methods
Pass Array Name into Method
int [] intArray = new int[100];
loadArray(intArray);
Accept into Method as an Array with No Set Size
void loadArray( int [] passedArray )
Changes to Array in Method *will* Update Original Array

10. public static void main(String [] args){
final int ASIZE = 5;
int [] intArray= new int[ASIZE];
for(int i = 0; i < ASIZE; i++)
intArray[i] = i;
System.out.println( intArray[0]);
changeZero(intArray); }
static void changeZero(int [] passedArray)
passedArray[0] = 1000;

11. Initializing Arrays char [] cArray3 = {'a', 'b', 'c'};
int [] iArray = {1, 2, 3, 4};
double [] dArray = {3.4, 5.67e4};

12. Two Dimensional Arrays
char [][] cArray = new char[10][20];
int [][] iArray = new int[100][50];
cArray[0][0] = ‘a’;
cArray[0][1] = ‘b’;
cArray[9][19] = ‘x’;
iArray[0][0] = 99;
iArray[1][5] = 135;
iArray[99][49] = 0;

13. Math Class Contains Typical Math Methods
In Package java.lang (i.e., automatically imported)
Access using Math.math_thing
Math.PI; Math.E (log e = 1)
double pow (double base, double exp)
double sqrt(double number)
int round(double number)
int abs( int number)
min(number1,number2) and max(number1, number2)
double random(); //random number between 0.0 and 1.0

14. Tokenizing/Parsing
Taking Apart a String and Separating It into Smaller Strings (i.e., “tokens”)
Usually, Tokens are Items Separated by Whitespace
Tokens Can Be Defined with Different Separators
Parsing Takes Tokens and Applies Some Manipulation of Those Tokens

15. StringTokenizer Class
import java.util.*; …
String bigString = “This is a sentence.”;
StringTokenizer st = new StringTokenizer(bigString);
while (st.hasMoreTokens()) {
System.out.println(st.nextToken()); }
// Displays This, is, a, and sentence. one
// per line

16. Static Variables and Methods
static means “in class” methods and variables
static variable: one per class (not one per object)
static method: no invoking object (invoke with className.method())

17. Static Variable Example
public class MyClass { …
private final int STARTID = 1;
private int IDNum = -1;
//above are one per object
private static int nextIDNum = STARTID;
//above is one per class
public MyClass() {
IDNum = nextIDNum;
nextIDNum++; }

18. Static Method Example public class MyClass { …
private final int STARTID = 1;
private int IDNum = -1;
//above are one per object
private static int nextIDNum = STARTID;
//above is one per class
public static int GetNextID() {
// Called by MyClass.GetNextID()
return nextIDNum; }

19. Other Class Methods boolean equals( objType comObj) void display()
compares invoking object with parameter of same type. Returns true if equal, false if not.
void display()
displays object to monitor
String toString()
converts each attirbute to String and returns String

20. Employee Class Review Create a Class Employee Employee.java
Employee Attributes (data members)
Constructor
Accessor Methods
Mutator Methods
toString() and equals()
tryEmployee.java (Client Test Program)

21. Final Exam
2 Hours
200 Points
35% of Grade
Must Take to Pass Course

22. Need to Know for Final Everything Through Exam 2 Plus: Arrays Methods
Classes
Constructors
Accessor Methods
Mutator Methods
toString() and equals() Methods

23. Final Exam 200 Points Total – 35% of Final Grade
90 points Matching or Short Answer or Multiple Choice (Terminology, Operators, JAVA Basics)
30 Points Program Output
80 Points Programming (Full Programs)