Java class1

1. Overriding

* Child

public class Child extends Parent {
  private void doSomething() {}

}

* Parent

public class Parent {
  public void doSomething() {}

}

* UseBoth

public class UseBoth {
  public void doOtherThing() {
    Parent p1 = new Parent();
    Parent p2 = new Child(); // illegal
    p1.doSomething();
    p2.doSomething();
  }

}

2.  Codes ID :-

*  Employee

public class Employee {

  private String name;

  private MyDate birthDate;

  private float  salary;

  // Constructor

  public Employee(String name, MyDate DoB, float salary) {

    this.name = name;

    this.birthDate = DoB;

    this.salary = salary;

  }

  public String getDetails() {

    return "Name: " + name + "\nSalary: " + salary

           + "\nBirth Date: " + birthDate;

  }

}

*  Manager

public class Manager extends Employee {

  private String department;

  public Manager(String name, MyDate DoB,

float salary, String dept) {

    super(name, DoB, salary);

    this.department = dept;

  }

  public String getDetail() {

    return super.getDetails() + "\nDepartment: " + department;

  }

}

*  MyDate

public class MyDate {

  private int day;

  private int month;

  private int year;

  public MyDate(int day, int month, int year) {

    this.day   = day;

    this.month = month;

    this.year  = year;

  }

  public boolean equals(Object o) {

    boolean result = false;

    if ( (o != null) && (o instanceof MyDate) ) {

      MyDate d = (MyDate) o;

      if ( (day == d.day) && (month == d.month)

  && (year == d.year) ) {

        result = true;

      }

    }

    return result;

  }

  public int hashCode() {

    return (day ^ month ^ year);

  }

}

*  TestEquals

public class TestEquals {

  public static void main(String[] args) {

    MyDate  date1 = new MyDate(14, 3, 1976);

    MyDate  date2 = new MyDate(14, 3, 1976);

    if ( date1 == date2 ) {

      System.out.println("date1 is identical to date2");

    } else {

      System.out.println("date1 is not identical to date2");

    }

    if ( date1.equals(date2) ) {

      System.out.println("date1 is equal to date2");

    } else {

      System.out.println("date1 is not equal to date2");

    }

    System.out.println("set date2 = date1;");

    date2 = date1;

    if ( date1 == date2 ) {

      System.out.println("date1 is identical to date2");

    } else {

      System.out.println("date1 is not identical to date2");

    }

  }

}

Code :-   https://drive.google.com/open?id=0B08RKBSts8D8T3BWTGpyQmNJeG8