object类的使用

/*object类，所有的类都继承object类tostring()对象的字符串的描述hashcode（）返回对象的哈希码equals()判断两个对象内容是否相等重写equals()方法，必须重写hashcode（）方法clone()创建并返回此对象的副本要想一个类的对象能够克隆，必须实现两点1：实现Cloneable接口（声明式接口，没要实现的方法）2：重写object继承的clone()方法*/class people implements Cloneable
{
    private String name;
    private int age;
    public people()
    {

    }
    public people(String name,int age)
    {
        this.name=name;
        this.age=age;

    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }

    public String toString() {  //重写父类的tostring(),不然返回对象名+哈希码（十六进制）
        return "name:"+this.getName()+",age"+this.getAge();
    }
    /*
    public String toString() {
        // TODO Auto-generated method stub
        return super.toString();
    }*/
    @Override
    public boolean equals(Object obj) {
        if (obj instanceof people) { //是否为people
            people people=(people) obj;
            if (this.getName().equals(people.getName())&&(this.getAge()==people.getAge())) {
                return true;
            }
            else {
                return false;
            }
        }
        else {
            return false;
        }

    }
    @Override
    public int hashCode() {
        // TODO Auto-generated method stub
        return this.getName().hashCode()+this.getAge();
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
        // TODO Auto-generated method stub
        return super.clone();
    }

}
public class main {

    public static void main(String[] args) {

        people aPeople=new people("jack", 23);
        System.out.println(aPeople); //[email protected],没重写tostring()
        System.out.println(aPeople); //name:jack,age23,重写tostring()
        System.out.println("aPeople的hashCode"+aPeople.hashCode());//aPeople的hashCode1508661727
        //打印出的是十进制的哈希码，和没重写tostring()方法的十六进制值相等
        //两个对象equales,他们的hashcode一定相等
        //两个对象不相等，他们的hangcode有可能相等

        people aPeople1=new people("jack", 23);//new的话是一个新对象
        System.out.println("aPeople1的hashCode"+aPeople1.hashCode());//aPeople1的hashCode1343958201

        System.out.println(aPeople==aPeople1);//地址不相同，返回false
        System.out.println(aPeople.equals(aPeople1));//返回false ？
        //说明：equals比较两者的内容是否相等，看上去两者内容相等，当没有重写它的equals方法时候，
        //默认比较的是他们的hashcode，对于上面2个对象，hashcode肯定不同，故返回false
        System.out.println(aPeople.equals(aPeople1));//重写equals后return true

        String a=new String("jack");
        String b=new String("jack");
        System.out.println(a==b); //return false;
        System.out.println(a.equals(b)); //return true;  ?
        System.out.println(a.hashCode()==b.hashCode()); //return true; ?
        //这边为什么又是true呢？因为String类(特殊的类)重写了hachcode和equals方法
        System.out.println(System.identityHashCode(a));
        System.out.println(System.identityHashCode(b)); //重写前的hashcode值是不同的

        //people p3=aPeople1; //这样clone的话p3改变的话对apeople1也有影响
        try {
            people p4=(people) aPeople1.clone();
            p4.setName("xiaoming");
            System.out.println(p4);  //这样的话是copy的副本，输出结果不一样
            System.out.println(aPeople1); //clone，改变p4对apeople1没影响
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

}