關於強制轉換

package net.test;

public class Test ...{

    public static void main(String[] args) ...{
        People people = new Student("zhangsan", Long.valueOf(2));
        People people2 = new People("lisi");

        if (people instanceof Student) ...{
            Student student = (Student) people;
            System.out.println(student.getName());
        } else ...{
            System.out.println("people無法進行強制轉換");
        }

        if (people2 instanceof Student) ...{
            Student student = (Student) people;
            System.out.println(student.getName());
        } else ...{
            System.out.println("people2無法進行強制轉換");
        }
    }

}

 

package net.test;

public class People ...{

    protected String name;

    public People() ...{
    }

    public People(String name) ...{
        this.name = name;
    }

    public String getName() ...{
        return name;
    }

    public void setName(String name) ...{
        this.name = name;
    }

}

 

package net.test;

public class Student extends People ...{

    private Long id;

    public Student(String name, Long id) ...{
        this.name = name;
        this.id = id;
    }

    public Long getId() ...{
        return id;
    }

    public void setId(Long id) ...{
        this.id = id;
    }

}