super() 有什么用?

super() 是调用父类的构造函数啦,如果在代码中无super()的话,还会不会调用父类的构造函数?

 

class Person {public static void prt(String s) {System.out.println(s);}Person() {prt("A Person.");}Person(String name) {prt("A person name is:" + name);}}

public class Chinese extends Person {Chinese() {super(); // 调用父类构造函数（1）prt("A chinese.");// (4)}Chinese(String name) {super(name);// 调用父类具有相同形参的构造函数（2）prt("his name is:" + name);}Chinese(String name, int age) {this(name);// 调用当前具有相同形参的构造函数（3）prt("his age is:" + age);}public static void main(String[] args) {Chinese cn = new Chinese();cn = new Chinese("kevin");cn = new Chinese("kevin", 22);}}

结果:

A Person.A chinese.A person name is:kevinhis name is:kevinA person name is:kevinhis name is:kevinhis age is:22

可见,子类在构造自己时会调用父类相关的构造函数的

super()就调用父类无参的构造函数

super(name)   父类1参数构造函数

this(name)   自己的1参数构造函数

 

如果不写super会如何?

public class Chinese extends Person {Chinese() {//super(); // 调用父类构造函数（1）prt("A chinese.");// (4)}Chinese(String name) {//super(name);// 调用父类具有相同形参的构造函数（2）prt("his name is:" + name);}Chinese(String name, int age) {//this(name);// 调用当前具有相同形参的构造函数（3）prt("his age is:" + age);}public static void main(String[] args) {Chinese cn = new Chinese();cn = new Chinese("kevin");cn = new Chinese("kevin", 22);}}

结果

A Person.A chinese.A Person.his name is:kevinA Person.his age is:22

可以看到子类还是会调用父类的构造函数,是无参数的那个构造函数