JavaBasic:继承

1. 继承是Java面向对象编程当中一种代码复用的方法
2. Java只允许单继承
3. proteced关键字把访问权限控制在子类与父类之间
4. 若父类的构造方法没有参数，子类可以默认调用；若父类的构造方法有参数，子类必须显示用super()调用父类的构造方法
5. 可以安全地向上转型为更为抽象的类型
6. 向下转型时最好用instanceof先判断

public class Person {
    protected String name;
    protected int age;
    protected String gender;

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


    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public void run(){
        System.out.println(name +" is running");
    }
}

public class Student extends Person {
    private int score;

    public Student(String name){
        /**
         * 必须显示地调用父类的构造方法
         */
        super(name);
        System.out.println("Student class create");
    }

    public int getScore() {
        return score;
    }

    public void setScore(int score) {
        this.score = score;
    }

    /**
     * 父类protecetd的属性允许被子类访问
     */
    public void hello(){
        System.out.println(this.gender);
    }
}

来源：CSDN

作者：weixin_45215505

链接：https://blog.csdn.net/weixin_45215505/article/details/104575411