【java】克隆clone()方法和相等equals()方法的重写

import java.util.Date;

public class House implements Cloneable {
     
        private int id;
        private double area;
        private Date whenBulit;
        House(){
        }
        House(int newId,double newArea){
            id = newId;
            area = newArea;
            whenBulit = new Date();
        }
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public void setArea(double area) {
            this.area = area;
        } 
        public void setWhenBulit(long whenBulit) {
           this.whenBulit.setTime(whenBulit) ;
        }    
        public double getArea() {
            return area;
        }
        public Date getWhenBulit() {
            return whenBulit;
        }
        public long getWhenBulitTime() {
            return whenBulit.getTime();
        }
       //重写equals方法，因为我们要对比的是date类中的时间而不是对象的引用地址
        public boolean equals(House obj){
            //obj.getArea()==this.getArea()
            //obj.getId()==this.getId();
            //obj.getWhenBuildTime==this.getWhenBuildTime()
            if(obj.getArea()==this.getArea()&&obj.getId()==this.getId()&&obj.getWhenBulitTime()==this.getWhenBulitTime())
              return true;
            else
            {
                return false;
            }
        }
        //如果重载了equals方法，按照规范也应该重载hashCode()，这里只是简单了将hashCode和传入的id关联起来
        @Override
        public int hashCode(){
            return getId();
        }
        public Object clone() throws CloneNotSupportedException{
            //构造一个对象 house,并且使用id和area
            House house = new House(this.getId(),this.getArea());
            //调用对象中的setWhenBuild方法，使用getTime()可以获得一个毫秒数。
            house.setWhenBulit(this.getWhenBulit().getTime()) ;
            return house ;
        }
    }

public class Testor {
     public static void main(String[] args ) throws CloneNotSupportedException{
            House h1 = new House(1,200.0);
            House h2 = (House)h1.clone();
            
            System.out.println(h1==h2);
            
            System.out.println(h1.equals(h2));
            
            System.out.println(h1.getWhenBulit()== h2.getWhenBulit());
            
            System.out.println(h1.getWhenBulit().equals(h2.getWhenBulit()));
        }
}

般情况下：

    x.clone().equals(x)

为 true，但这并非必须要满足的要求。

public class TestClone implements Cloneable {

    public static void main(String []args) throws CloneNotSupportedException{
        TestClone tc=new TestClone();
        try{
        Object obj=tc.clone();
        System.out.println(obj==tc);//结果是false
        System.out.println(obj.equals(tc));//结果是false
        }catch(Exception e){
            System.out.println("Exception:"+e.getMessage());
        }
    }
}