Equals比较对象

来源：互联网发布：中学生网络交友情况编辑：程序博客网时间：2024/09/21 09:02

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；

0 0