equals hashcode toString 方法的使用

package com.wu.toString;

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

/**
 *
 * @author wuyong
 * @email 382999338@qq.com
 * @date2016年9月1日下午4:39:09
 * 雇员类
 */
class Employee
{
       private String name;
       private double salary;//薪水
       private Date hireDay;//入职时间
    //构造方法：主要作用是初始化参数
   public Employee(String n, double s, int year, int month, int day)
   {
      name = n;
      salary = s;
      GregorianCalendar calendar = new GregorianCalendar(year, month - 1, day);
      hireDay = calendar.getTime();
   }

   public String getName()
   {
      return name;
   }

   public double getSalary()
   {
      return salary;
   }

   public Date getHireDay()
   {
      return hireDay;
   }

   public void raiseSalary(double byPercent)
   {
      double raise = salary * byPercent / 100;
      salary += raise;
   }
   /*
    * equals方法：用户检测一个对象是否等于另外一个对象。(non-Javadoc)
    * 在Object类中，这个方法将判断两个对象是否具有相同的引用。
    * @see java.lang.Object#equals(java.lang.Object)
    */

   public boolean equals(Object otherObject)
   {
      // a quick test to see if the objects are identical
       //如果Employee与参数otherObjectd的引用的对象相同，返回true
      if (this == otherObject) return true;

      // must return false if the explicit parameter is null
      //如果参数为空返回的是false
      if (otherObject == null) return false;

      // if the classes don't match, they can't be equal
      //如果Employee与otherObject类型不同，返回false
      if (getClass() != otherObject.getClass())
         return false;

      // now we know otherObject is a non-null Employee
      //将otherObject强制转换为Employee类型
      Employee other = (Employee) otherObject;

      // test whether the fields have identical values
      return name.equals(other.name)//可以写成this.name.equals(other.name)
         && salary == other.salary
         && hireDay.equals(other.hireDay);
   }
   /*
    * ashCode方法：散列码是由对象导出的一个整型值。没有规律(non-Javadoc)
    * @see java.lang.Object#hashCode()
    */
   public int hashCode()
   {
      return 7 * name.hashCode()
         + 11 * new Double(salary).hashCode()
         + 13 * hireDay.hashCode();
   }
   /*
    * toString方法：用于返回表示对象值得字符串(non-Javadoc)
    * @see java.lang.Object#toString()
    */
   public String toString()
   {
      return getClass().getName()
         + "[name=" + name
         + ",salary=" + salary
         + ",hireDay=" + hireDay
         + "]";
   }
}

package com.wu.toString;

/**
 * 经理类，继承雇员类
 * @author wuyong
 * @email 382999338@qq.com
 * @date2016年9月1日下午4:37:51
 */

class Manager extends Employee
{
    private double bonus;//奖金

   public Manager(String n, double s, int year, int month, int day)
   {
      super(n, s, year, month, day);
      bonus = 0;
   }
   //计算薪水
   public double getSalary()
   {
      double baseSalary = super.getSalary();//调用父类的方法
      return baseSalary + bonus;
   }

   public void setBonus(double b)
   {
      bonus = b;
   }

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

   public int hashCode()
   {
      return super.hashCode()
         + 17 * new Double(bonus).hashCode();
   }

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

}

package com.wu.toString;
/**
 *
 * @author wuyong
 * @email 382999338@qq.com
 * @date2016年9月1日下午4:33:20
 * 测试类
 *
 */
import java.util.*;

public class EqualsTest
{
   public static void main(String[] args)
   {
      Employee alice1 = new Employee("Alice Adams", 75000, 1987, 12, 15);
      Employee alice2 = alice1;
      Employee alice3 = new Employee("Alice Adams", 75000, 1987, 12, 15);
      Employee 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);

      Manager carl = new Manager("Carl Cracker", 80000, 1987, 12, 15);
      Manager 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());
   }
}