This section focuses on overriding equals() and hashCode().

Employee class

import java.time.*;
import java.util.Objects;

public class Employee
{
   private String name;
   private double salary;
   private LocalDate hireDay;

   public Employee(String name, double salary, int year, int month, int day)
   {
      this.name = name;
      this.salary = salary;
      hireDay = LocalDate.of(year, month, day);
   }

   public String getName(a)
   {
      return name;
   }

   public double getSalary(a)
   {
      return salary;
   }

   public LocalDate getHireDay(a)
   {
      return hireDay;
   }

   public void raiseSalary(double byPercent)
   {
      double raise = salary * byPercent / 100;
      salary += raise;
   }
   / / to equals
   public boolean equals(Object otherObject)
   {
      // a quick test to see if the objects are identical
      if (this == otherObject) return true;

      // must return false if the explicit parameter is null
      if (otherObject == null) return false;

      // if the classes don't match, they can't be equal
      if(getClass() ! = otherObject.getClass())return false;

      // now we know otherObject is a non-null Employee
      var other = (Employee) otherObject;

      // test whether the fields have identical values
      return Objects.equals(name, other.name) 
         && salary == other.salary && Objects.equals(hireDay, other.hireDay);
   }

   public int hashCode(a)
   {
      return Objects.hash(name, salary, hireDay); 
   }

   public String toString(a)
   {
      return getClass().getName() + "[name=" + name + ",salary=" + salary + ",hireDay=" 
         + hireDay + "]"; }}Copy the code

Manager class

The following code shows how to write in a subclassequals()andhashCode()

public class Manager extends Employee
{
   private double bonus;

   public Manager(String name, double salary, int year, int month, int day)
   {
      super(name, salary, year, month, day);
      bonus = 0;
   }

   public double getSalary(a)
   {
      double baseSalary = super.getSalary();
      return baseSalary + bonus;
   }

   public void setBonus(double bonus)
   {
      this.bonus = bonus;
   }

   public boolean equals(Object otherObject)
   {
      if (!super.equals(otherObject)) return false;
      var other = (Manager) otherObject;
      // super.equals checked that this and other belong to the same class
      return bonus == other.bonus;
   }

   public int hashCode(a)
   {
      return java.util.Objects.hash(super.hashCode(), bonus);
   }

   public String toString(a)
   {
      return super.toString() + "[bonus=" + bonus + "]"; }}Copy the code

EqualsTest class

/**
 * This program demonstrates the equals method.
 * @versionThe 2012-01-26 * 1.12@author Cay Horstmann
 */
public class EqualsTest
{
   public static void main(String[] args)
   {
      var alice1 = new Employee("Alice Adams".75000.1987.12.15);
      var alice2 = alice1;
      var alice3 = new Employee("Alice Adams".75000.1987.12.15);
      var bob = new Employee("Bob Brandson".50000.1989.10.1);

      System.out.println("alice1 == alice2: " + (alice1 == alice2));

      System.out.println("alice1 == alice3: " + (alice1 == alice3));

      System.out.println("alice1.equals(alice3): " + alice1.equals(alice3));

      System.out.println("alice1.equals(bob): " + alice1.equals(bob));

      System.out.println("bob.toString(): " + bob);

      var carl = new Manager("Carl Cracker".80000.1987.12.15);
      var boss = new Manager("Carl Cracker".80000.1987.12.15);
      boss.setBonus(5000);
      System.out.println("boss.toString(): " + boss);
      System.out.println("carl.equals(boss): " + carl.equals(boss));
      System.out.println("alice1.hashCode(): " + alice1.hashCode());
      System.out.println("alice3.hashCode(): " + alice3.hashCode());
      System.out.println("bob.hashCode(): " + bob.hashCode());
      System.out.println("carl.hashCode(): "+ carl.hashCode()); }}Copy the code