java基础篇（十二）——构造函数和子类构造函数

class Person {private int age;public void setAge(int age) {if (age < 0 || age > 200)age = 0;else {this.age = age;}}public int getAge() {return age;}
/*父类的无参构造函数*/
 public Person () {System.out.println("Person ()");}
/*父类的有参构造函数，当提供了有参构造函数的时候，最后提供一个无参构造函数，
因为当提供了有参构造函数之后，系统就不会自动提供无参构造函数了*/
 public Person (int age) {System.out.println("Person (int age)");this.age = age;}}class Student extends Person{private String school;public void setSchool(String school) {this.school = school;}public String getSchool() {return school;} /*子类的有参构造函数，最后提供一个无参构造函数，读者可以自己试一下，*/public Student(String school) {/* will call the super() *///super();/*子类先调用父类的构造函数，后调用子类的构造函数，无参构造，默认*/super(5);/*子类调用父类的有参构造函数*/System.out.println("Student(String school)");this.school = school;}}public class Ext4 {public static void main (String args[]) {Student stu = new Student("ustc");//stu.setAge(10);System.out.println(stu.getAge());System.out.println(stu.getSchool());}}