Java类型转化

public class User {
    private long id;
    private String name="zs";
    private String password;

	//提供无参、有参构造方法。setter，getter方法。覆写toString方法。
}

public class Student {
    private Long id;
    private String name;
    private String password;

	//提供无参、有参构造方法。setter，getter方法。覆写toString方法。
}

public class ClassCastTest {
    public static void main(String[] args) {
        User user = new User(1L,"zs","1234567");
        Student student = (Student)user;//编译报错
    }
}

public class ClassCastTest {
    public static void main(String[] args) {
        Object object = new User(1L,"zs","1234567");//小转大，自动隐式转化
        User user = (User)object;//大转小，强制转化
        System.out.println(user);//User{id=1, name='zs', password='1234567'}
    }
}

public class ClassCastTest {
    public static void main(String[] args) {
        Object object = new User(1L,"zs","1234567");
        Student student = (Student)object;//java.lang.ClassCastException
    }
}

public class ClassCastTest {
    public static void main(String[] args) {
        Object object = new User(1L,"zs","1234567");
        cast(object);//User{id=1, name='zs', password='1234567'}
        User user = new User();
        cast(user);//User{id=0, name='null', password='null'}

        Object object2 = new Student(1L,"xxs","666");
        cast(object2);//Student{id=1, name='xxs', password='666'}
        cast(new Student());//Student{id=null, name='null', password='null'}

        cast("12345");//不属于User或者Student类型
    }

    private static void cast(Object object){
        if (object instanceof User){
            User user = (User)object;
            System.out.println(user);
        }else if(object instanceof Student){
            Student student = (Student)object;
            System.out.println(student);
        }else {
            System.out.println("不属于User或者Student类型");
        }
    }
}

public class ClassCastTest {
    public static void main(String[] args) {
        Object object = new User(1L,"zs","1234567");
        cast(object);//User{id=1, name='zs', password='1234567'}
        User user = new User();
        cast(user);//User{id=0, name='null', password='null'}

        Object object2 = new Student(1L,"xxs","666");
        cast(object2);//Student{id=1, name='xxs', password='666'}
        cast(new Student());//Student{id=null, name='null', password='null'}

        cast("12345");//不属于User或者Student类型
    }

    private static void cast(Object object){
        if (object.getClass()==User.class){
            User user = (User)object;
            System.out.println(user);
        }else if(object.getClass()==Student.class){
            Student student = (Student)object;
            System.out.println(student);
        }else {
            System.out.println("不属于User或者Student类型");
        }
    }
}

public class ClassCastTest {
    public static void main(String[] args) {
        Object object = new User(1L,"zs","1234567");
        cast(object);//User{id=1, name='zs', password='1234567'}
        User user = new User();
        cast(user);//User{id=0, name='null', password='null'}

        Object object2 = new Student(1L,"xxs","666");
        cast(object2);//Student{id=1, name='xxs', password='666'}
        cast(new Student());//Student{id=null, name='null', password='null'}

        cast("12345");//不属于User或者Student类型
    }

    private static void cast(Object object){
        if(User.class.equals(object.getClass())){
            User user = (User)object;
            System.out.println(user);
        }else if(Student.class.equals(object.getClass())){
            Student student = (Student)object;
            System.out.println(student);
        }else {
            System.out.println("不属于User或者Student类型");
        }
    }
}