继承简单例子

class Person{
	String name;
	int age;

	Person(){
		System.out.println("Person无参数构造函数");
	}

	Person(String name,int age){
		this.name = name;
		this.age = age;
		System.out.println("Person有参数构造函数");
	}
	void eat(){
		System.out.println("吃饭");
	}
}

class Student extends Person{
	String grade;
	Student(){
		System.out.println("Student的无参数构造函数");
	}
	Student(String name,int age,String grade){
		super(name,age);
		this.grade = grade;
	}
}

class Test{
	public static void main(String[] args){
		Student stu = new Student("haha",6,"xueqianban");
		System.out.println("name:"+stu.name+"\n"+"age:"+stu.age+"\n"+"grade:"+stu.grade);
	}
}

子类的构造函数中，编译器会默认的加一个super()父类构造函数。