instanceof和类型转换

1. 类型转换

• • 　父类引用转向子类对象
  • 把子类转换为父类，向上转型
  • 把父类转换为子类，向下转型，强制转换
  • 方便方法的调用

    public static void main(String[] args) {
        //instanceof
       // Object->Person->Student
//       Object object=new Student();
//        System.out.println(object instanceof Student);
//        System.out.println(object instanceof Person);
//        System.out.println(object instanceof Object);
//        System.out.println(object instanceof Teacher);
//        System.out.println(object instanceof String);

        //Person->Student
//        Student student=new Student();
//        System.out.println(student instanceof Student);
//        System.out.println(student instanceof Person);
//        System.out.println(student instanceof Object);
       // System.out.println(student instanceof Teacher);

        Person person1=new Student();  //父亲--->>子类
        //person将这个对象转化为Student类型，我们就可以使用Student类型的方法了
         Student student= (Student) person1;
         student.eat();

        ((Student) person1).eat();
        //子类转父类可能丢失原来子类的方法
       // Student student1=new Student();
       // Person person=student1;
        //person.eat;//无法再调用自己的eat