public class Main
{
    private static Employee[] staff;

    public static void main(String[] args){
        Employee h1 = new Hourly(100, "f1", "L1", 20.0, 12.50);
        //polymorphic demo of our class design
        // Employee[] staff = new Employee[3];

        // staff[0] = new Hourly(100, "f1", "L1", 20.0, 12.50);
        // staff[1] = new Salary(200, "f2", "L2", 65000);
        // staff[2] = new Hourly(101, "f3", "L3", 40.0, 15.50);

            staff = new Employee[]{
            new Hourly(100, "f1", "L1", 20.0, 12.50),
            new Salary(200, "f2", "L2", 65000),
            new Hourly(101, "f3", "L3", 40.0, 15.50)
        };

        for (Employee e : staff){
            System.out.printf("%s%.2f%n", "Employee paycheck: $", e.paycheck() );
        }

        for (Employee e : staff){
            if ( e instanceof Hourly){
                Hourly h = (Hourly) e;
                System.out.println("Hours worked this week: " + h.getHoursPerWeek() );
            } else if (e instanceof Salary){
                Salary s = (Salary) e;
                System.out.println("Annual compensation: " + s.getAnnualSalary() );
            }
        }

        System.out.printf("h1 present? %s", contains(h1) );
    }

    public static boolean contains(Employee o){
        // for (int i = 0; i <= staff.length - 1; i++){
            // if (staff[i].equals(o) ){
                // return true;
            // }
        // }

        for (Employee e : staff){
            if (e.equals(o) ){
                return true;
            }
        }
        return false;
    }
}



import java.util.Objects;

public abstract class Employee
{
    protected int sid;
    protected String first;
    protected String last;

    public Employee(int sid, String first, String last){
        setSid(sid);
        setFirst(first);
        setLast(last);
    }

    public final int getSid() {return sid;}
    public final String getFirst() {return first;}
    public final String getLast() {return last;}

    public final void setSid(int sid) {this.sid = sid;}
    public final void setFirst(String first) {this.first = first;}
    public final void setLast(String last) {this.last = last;}

    /* Overwrite the equals method. Use the @Override annotation from here on our when overwriting */
    @Override
    public boolean equals(Object o){
        if ( o == null){ return false;}
        else if (this.getClass() != o.getClass() ) {return false;}
        else if (this == o){return true;}
        else{
            Employee that = (Employee) o;
            return Objects.equals(this.sid, that.sid) && Objects.equals(this.first, that.first) &&
            Objects.equals(this.last, that.last);
        }
    }

    //this method is required to be implemented by all subclasses
    public abstract double paycheck();

    @Override
    public String toString(){
       String str = "";

       //Note the getClass().getCanonicalName() display's objects class name
       str += String.format("%s: [%d][%s, %s]", getClass().getCanonicalName(), sid, first, last);
       return str;
    }
 }



import java.util.Objects;

public class Salary extends Employee{
   protected double annualSalary;

    public Salary(int sid, String first, String last, double annualSalary){
        super(sid, first, last);
        setAnnualSalary(annualSalary);
   }

   public final double getAnnualSalary() {return annualSalary;}
   public final void setAnnualSalary(double annualSalary) {this.annualSalary = annualSalary;}

   @Override
   public double paycheck(){
       return annualSalary / 26.0;
    }

   public boolean equals(Salary o){
        String thisName = last + " " + first;
        String oName = o.last + " " + o.first;

        return thisName.equals(oName);
    }

   @Override
   public boolean equals(Object o){
       if ( o == null){ return false;}
        else if (this.getClass() != o.getClass() ) {return false;}
        else if (this == o){return true;}
        else{
            Salary that = (Salary) o;
            return super.equals(o) && Objects.equals(this.annualSalary, that.annualSalary);
        }
    }

   @Override
   public String toString(){
       String str = "";

       str += String.format("%s[$%.0f][Paycheck: $%.2f]", super.toString(), annualSalary, paycheck());
       return str;
    }
}



import java.util.Objects;

public class Hourly extends Employee{
    protected double hoursPerWeek;
    protected double payPerHour;

    public Hourly(){
        this(0, "N/a", "N/a", 0.0, 0.0);
    }
    public Hourly(int sid, String first, String last, double hoursPerWeek, double payPerHour){
        super(sid, first, last);
        setHoursPerWeek(hoursPerWeek);
        setPayPerHour(payPerHour);
    }

    public final double getHoursPerWeek(){ return hoursPerWeek; }
    public final double getPayPerHour(){ return payPerHour; }

    public final void setHoursPerWeek(double hoursPerWeek){ this.hoursPerWeek = hoursPerWeek; }
    public final void setPayPerHour(double payPerHour){ this.payPerHour = payPerHour; }

    @Override
    public double paycheck(){
        return hoursPerWeek * payPerHour;
    }

    public boolean equals(Hourly o){
        String thisName = last + " " + first;
        String oName = o.last + " " + o.first;

        return thisName.equals(oName);
    }

    @Override
    public boolean equals(Object o){
       if ( o == null){ return false;}
        else if (this.getClass() != o.getClass() ) {return false;}
        else if (this == o){return true;}
        else{
            Hourly that = (Hourly) o;
            return super.equals(o) && Objects.equals(this.hoursPerWeek, that.hoursPerWeek) &&
            Objects.equals(this.payPerHour, that.payPerHour);
        }
    }

    @Override
    public String toString(){
       String str = "";

       str += super.toString();
       str += String.format("[%.1f, $%.2f][Paycheck: $%.2f]", hoursPerWeek, payPerHour, paycheck());
       return str;
    }
}



public class Student{

   private int sid;
   private String first;
   private String last;
   private String academicYear;
   //Two memory types = stack and heap(free store)
   // cds = designated constructor calls the setter, the others are the convenience ctrs - call designated
   public Student(){
       this(0, "N/A", "N/A", "N/A");
   }
   //Student me = new Student(); me is an object reference of the Student() object
   //me is a part of the static context, the stack whereas the object is part
   //of the dynamic memory, the heap
   public Student(int sid, String first, String last){
       this(sid, first, last, "N/A");
   }
   //me.getFirst(), me is the receiving object
   //designated ctor
   public Student(int sid, String first, String last, String academicYear){
       setSid(sid);
       setFirst(first);
       setLast(last);
       setAcademicYear(academicYear);
   }
   //this is a reference
   public int getSid()          { return sid; }
   public String getFirst()     { return first; }
   public String getLast()      { return last; }
   public String getAcademicYear()     { return academicYear; }
   //Value types = primitive --> int, double vs reference --> Class objects
   public void setSid(int sid){
       if (sid > 0){
           this.sid = sid;
        }
    }
   public void setFirst(String first)  { this.first = first; }
   public void setLast(String last)    { this.last = last; }
   public void setAcademicYear(String academicYear){
       switch (academicYear.toUpperCase() ){
           case "FR":
           case "SO":
           case "JR":
           case "SR":
                this.academicYear = academicYear;
                break;
            }
    }

   public String toString() {
       String str = "";

       str += "(" + sid + ")" + "[" + first + " " + last + "]" + " - " + academicYear;
       return str;
    }
}



import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;

public class Main{
    private static final int MAX_STUDENTS = 5;
    private static Student[] students = new Student[MAX_STUDENTS];
    private static int numberOfStudents;

   public static void main(String[] args){
       try{
           loadStudentsFromFile("students.txt");
           writeStudentsToFile("studentsOut.txt");
           displayStudents();

        } catch(FileNotFoundException e){
           System.err.println( e.getMessage() );
           System.exit(1);
        }
    }

   public static void loadStudentsFromFile(String fileName) throws FileNotFoundException{
       try (Scanner fs = new Scanner(new File(fileName)); ){
           String record = "";
           String[] fields = null;;
           int count = 0;

           int sid;
           String first;
           String last;
           String academicYear;

           while (fs.hasNext() ){
               record = fs.nextLine();
               fields = record.split(",");

               //extract the fields into the local vars
               sid = Integer.parseInt(fields[0]);
               first = fields[1];
               last = fields[2];
               academicYear = fields[3];

               students[count++] = new Student(sid, first, last, academicYear);
            }
        }
    }

   public static void writeStudentsToFile(String fileName) throws FileNotFoundException{
       try (PrintWriter pw = new PrintWriter(new File(fileName)); ){
           for (Student s : students){
               pw.println(s);
            }
    }
  }

   public static void displayStudents(){
       for (Student s : students){
               System.out.println(s);
            }
    }
}