相等测试与继承

import java.util.Date;
import java.util.GregorianCalendar;

class Employee {
    private String name;
    private double salary;
    private Date hireDay;
    public Employee(String n, double s, int year, int month, int day) {
        name = n;
        salary = s;
        GregorianCalendar calendar = new java.util.GregorianCalendar(year,
                month - 1, day);
        hireDay = calendar.getTime();
    }

    public Date getHireDay() {
        return hireDay;
    }

    public String getName() {
        return name;
    }

    public double getSalary() {
        return salary;
    }

    public void setHireDay(Date hireDay) {
        this.hireDay = hireDay;
    }

    public void raiseSalary(double byPercent) {
        double raise = salary * byPercent / 100;

        salary = raise;
    }
    

    //重写equals()
    public boolean equals(Object otherOb) {
        if (this == otherOb) {
            return true;
        }
        if (otherOb == null) {
            return false;
        }
        if (this.getClass() != otherOb.getClass()) {
            return false;
        }
        Employee other = (Employee) otherOb;

        return name.equals(other.name) && salary == other.salary &&
                hireDay.equals(other.hireDay);
    }
    //重写hashCode()
    public int hashCode() {
        return 7 * name.hashCode() + 11 * new Double(salary).hashCode() +
                13 * hireDay.hashCode();
    }
    //个性化toString()
    public String toString() {
        return getClass().getName()
                + "[name=" + name + ",salary=" + salary + ",hireDay=" + hireDay +
                "]";
    }

}

public class Manager extends Employee {
    private double bonus;
    public Manager(String n, double s, int year, int month, int day) {
        super(n, s, year, month, day); //实现基类构造方法
        bonus = 0;
    }


    public static void main(String[] args) {
    }

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

    public void setBonus(double bonus) {
        this.bonus = bonus;
    }
    //重写equals()
    public boolean equals(java.lang.Object otherOb) {
        if (!super.equals(otherOb)) {
            return false;
        }
        Manager other = (Manager) otherOb;
        return bonus == other.bonus;
    }
   //重写hashCode
    public int hashCode() {
        return super.hashCode()
                + 17 * new Double(bonus).hashCode();
    }
    //实现父类toString增加bonus
    public String toString() {
        return super.toString() + "[bonus=" + bonus + "]";
    }

}

/**
* <p>Title: </p>
*
* <p>Description: </p>
*
* <p>Copyright: Copyright (c) 2007</p>
*
* <p>Company: </p>
*
* @author not attributable
* @version 1.0
*/
public class EqualsTest {
    public static void main(String[] args) {
        EqualsTest equalstest = new EqualsTest();

        Employee alice1 = new Employee("jingjing", 7500, 1987, 12, 15);
        Employee alice2 = alice1;
        Employee alice3 = new Employee("jingjing", 7500, 1987, 12, 15);
        Employee bob = new Employee("Zhangfan", 5000, 1989, 10, 1);
        //user ==
        System.out.println("alicel==alice2:" + (alice1 == alice2));
        System.out.println("alicel==alice3:" + (alice1 == alice3));
        //user equals
        System.out.println("alice1.equals(alice3):" + alice1.equals(alice3));
        System.out.println("alice1.equals(bob):" + alice1.equals(bob));

        System.out.println("bob.toString():" + bob);
       //S.OP(bob)先调用Object的toString().但该方法被子类重构了,所以相当于bob.toString()

        Manager carl = new Manager("Carl Cracker", 8000, 1987, 12, 15);
        Manager boss = new Manager("Carl Cracker", 8000, 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());

    }
}