导出类和基类构造器的初始化

在创建导出类的对象时，基类的构造器总会被调用，并且在导出类构造器之前调用。一般在导出类的构造器里调用基类的构造器。

public class A {
A(){
System.out.println("A constructor");
}

A(int i){
System.out.println(i);
}

public static void main(String[] args) {
AAA ex1 = new AAA();
AAA ex2 = new AAA(3);
}
}

class AA extends A{

AA(){
System.out.println("AA constructor");
}
AA(int i){
super(1);
System.out.println(i);
}
}

class AAA extends AA{
AAA(){
System.out.println("AAA constructor");
}

AAA(int i){
super(2);
System.out.println(i);
}
}

output:

A constructor
AA constructor
AAA constructor
1
2
3