为什么在子类构造函数中调用“super()”？

Question

Why do I need to call super here?

class Animal {
    public Animal(String arg) {
        System.out.println("Constructing an animal: " + arg);
    }
}

class Dog extends Animal {
    public Dog() {
        super("From Dog constructor");
        System.out.println("Constructing a dog.");
    }
}

Answer 1

If the parent constructor has no argument, no reason whatsoever. Otherwise, you need an explicit call to super(...) where you can set those parameters.

Answer 2

By default every class having default constructor ie non parameterized constuctor, once you define any constructor on it then default behavour will not work.

Another thing is if any class extends any other class then by default each constructor of child class will call their parrent's default constructor ie super() internally but once you declare parameterized constuctor to the parent class then you need to call it from child class constructor explictly ie super(parameter...)