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

2. 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;

3. Classes A Class Is an Object Type
A Class Represents a “Thing” (e.g., employee, wrench, list, store, shopping cart, etc.)
Service Class – Class used by Other Programs
Programmers Define Classes with Data Members (or Fields) and Methods
Must Be Created in ClassName.java File
Client Program – Program using a class

4. Access Modifiers Used to Identify What May Use Methods
public – any method may use (Usually methods)
private – only methods in same class may use (usually data members)

5. Designing a Class Decide How It Will Be Used
Decide on Interface (i.e., public representation, public methods)
Decide on Implementation (i.e., private data and data manipulation)

6. Example Class
Class Employee
firstName
lastName
salary

7. Constructor Class Method of Same Name
Example: class Employee Method Employee()
Called When Variable Declared (instantiated) of Class Type
Initializes Instantiated Object
May Have Multiple Constructors Each with Different Parameters

8. class Employee // Employee.java{
private String firstName;
private String lastName;
private double salary;
public Employee()
firstName = "NoFirstName";
lastName = "NoLastName";
salary = 0.0; }

9. Accessor Methods
Public Methods for Getting Attributes of Class

10. public String GetLastName() return lastName; public double GetSalary()
class Employee {
private String firstName;
private String lastName;
private double salary;
public Employee()
firstName = "NoFirstName";
lastName = "NoLastName";
salary = 0.0; }
public String GetFirstName()
return firstName;
public String GetLastName()
return lastName;
public double GetSalary()
return salary;

11. Client Program A Program that Uses a Class Is a Client of that Class
Class Objects are Declared and Instantiated Using the new keyword.
new ClassName(parameters) Calls Constructor for Class
Class Public Methods Called Using Dot (e.g., variable.GetFirstName();)

12. class useEmployee //useEmployee.java{
public static void main(String [ ] args)
Employee emp1 = new Employee();
System.out.println("Name is" emp1.GetFirstName() + " " + emp1.GetLastName()); }
firstName
emp1
“NoFirstName”
lastName
“NoLastName”
salary
0.0

13. Mutator Methods
Class Methods Used to Modify a Class Object are Called Mutator Methods
Allows Restricted Manipulation of Class Object Data

14. public boolean SetSalary(double passedSalary){
if (salary <= MAXSALARY)
salary = passedSalary;
return true; }
else
return false;

15. class useEmployee if (emp1.SetSalary(55000)){
public static void main(String [ ] args)
Employee emp1 = new Employee();
System.out.println("Name is" + emp1.GetFirstName() + " " + emp1.GetLastName());
if (emp1.SetSalary(55000))
System.out.println("Salary set to 55000"); }
else
System.out.println("Salary not set");