package com.c2;public class Ext {	public static void main(String[] args) {		Student s = new Student();		System.out.println(s.name);		System.out.println(s.age);	}}package com.c2;public class Person {	int age;	String name = "zhangsan";	Person() {	}	public Person(int a) {		age = a;	}}package com.c2;public class Student extends Person {	public Student() {	}	public Student(int a) {		super(23);	}}

　　总结：构造函数必须带着，重写发生在子类继承父类里，继承是子类调用父类的属性或方法，重写时方法名称，及参数列表都得相同，但方法体内容不相同，super关键字是调用父类里的方法