Object Oriented principles

4 principles of OOPs
Inheritance--general-->more specific--code reuse
Encapsulation--seperation of concerns--every class should be self 
contained, as few dependencies as possible
Polymorphism--adapt and behave differently depending on environment
--overloading methods, overriding methods--generics
Abstraction--generalize, group everthing that is common

4 Types of Relationships
Inheritance
Association
Composition
Aggregation

Here is the diagram that shows the inheritance hierarchy

Here are the code classes that show that inheritance

Person Class

package com.spconger;

public abstract class Person {
 private String number;
 private String name;
 private String email;
 private String phone;
 
 public String getNumber() {
  return number;
 }
 public void setNumber(String number) {
  this.number = number;
 }
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }
 public String getEmail() {
  return email;
 }
 public void setEmail(String email) {
  this.email = email;
 }
 public String getPhone() {
  return phone;
 }
 public void setPhone(String phone) {
  this.phone = phone;
 }

}

The Customer Class

package com.spconger;

import java.util.ArrayList;

public class Customer extends Person{
 ArrayList<String> coupons = new ArrayList<String>();
    public void AddCoupons(String coupon){
     coupons.add(coupon);
    }
    public String toString(){
     return getName();
    }
}

The EmployeeClass

package com.spconger;

public abstract class Employee extends Person {
  private String position;
  private String hireDate;
public String getPosition() {
 return position;
}
public void setPosition(String position) {
 this.position = position;
}
public String getHireDate() {
 return hireDate;
}
public void setHireDate(String hireDate) {
 this.hireDate = hireDate;
}
  public double calculatePay(){
   return 0.0;
  }
}

The SalaryEmployee Class

package com.spconger;

public class SalaryEmployee extends Employee{
 private double salary;

 public double getSalary() {
  return salary;
 }

 public void setSalary(double salary) {
  this.salary = salary;
 }
 
 public double calculatePay(){
  return getSalary()/12;
 }
 
}

Program Class

package com.spconger;

import java.util.Scanner;

public class Program {

 public static void main(String[] args) {
  // TODO Auto-generated method stub
  Customer c = new Customer();
  c.setName("George");
  
  SalaryEmployee se = new SalaryEmployee();
  se.setName("Jenny");
  se.setSalary(30000.00);
  
  System.out.println(se.getName() + "," + se.getSalary() 
  + ", " + se.calculatePay());
  
  System.out.println(c.toString());
 }

}

Composition and Aggregation Diagrams