Equals比较对象

package test;

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

public class EqualTest{

public static void main(String[] args){
Employee a1 = new Employee("adams", 75000, 1987, 12, 15);
Employee a2 = a1;
Employee a3 = new Employee("adams", 75000, 1987, 12, 15);
Employee bob = new Employee("bob", 50000, 1989, 10, 1);

System.out.println("a1==a2:" + (a1==a2));
System.out.println("a1==a3:"+(a1==a3));
System.out.println("a1.equals(a3):"+a1.equals(a3));
System.out.println("a1.equals(bob):"+a1.equals(bob));
System.out.println("bob.toString():"+bob);

Manager car1 = new Manager("Car Cracker",80000,1987,12,15);
Manager boss = new Manager("Car Cracker",80000,1987,12,15);
boss.setBonus(5000);
System.out.println("boss.toString():" + boss);
System.out.println("car1.equals(boss):"+ car1.equals(boss));
System.out.println("a1.hashCode():" + a1.hashCode());
System.out.println("a3.hashCode():" + a3.hashCode());
System.out.println("bob.hashCode():"+ bob.hashCode());
System.out.println("car1.hashCode():"+ car1.hashCode());
}
}

class Employee{

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();
}

private String name;
private Double salary;
private Date hireDay;

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;
}

public boolean equals(Object otherObject){
if(this == otherObject) return true;

if(otherObject == null) return false;

if(getClass() != otherObject.getClass()) return false;

Employee other = (Employee) otherObject;

return name.equals(other.name) && salary == other.salary && hireDay.equals(other.hireDay);
}

public int hashCode(){
return 7*name.hashCode() + 11 * new Double(salary).hashCode() + 13 * hireDay.hashCode();
}

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

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);
bonus = 0;
}

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

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

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

}

结果为：

a1==a2:true

a1==a3:false

a1.equals(a3):false

a1.equals(bob):false

bob.toString():test.Employee[name=bob,salary=50000.0,hireDay=Sun Oct 01 00:00:00 CST 1989]

boss.toString():test.Manager[name=Car Cracker,salary=80000.0,hireDay=Tue Dec 15 00:00:00 CST 1987][bonus=5000.0]

car1.equals(boss):false

a1.hashCode():-1671370621

a3.hashCode():-1671370621

bob.hashCode():53370192

car1.hashCode():-1609448924

个人小结：

总结：equals方法是用来判断两个对象是否是相等的，如果连个对象指向同一块存储区域中，方法返回true；否则方法返回false；