继承

/*java是单继承的，只能继承与一个类，如果没有显示指明继承，则默认继承于Object，扩展的话，需要通过接口；*///继承示例class ExtendsDemo{public static void main(String[] args) {   Student s=new Student();   s.name="zhangsan";   s.age=20;   System.out.println(s.name+":"+s.age);   Worker w=new Worker();   w.name="lisi";   w.age=30;   System.out.println(w.name+":"+w.age);}}//人类class Person{ String name; int age;}//学生类class Student extends Person{      //System.out.println("student");}//工人类class Worker{//System.out.println("work");}