什么时候应该从子类中调用超类的构造函数？

Question

The statement that calls the constructor of the superclass should be the last statement in the constructor of a subclass.

Is it a valid statement?

Answer 1

No, It should be the first statement of the sub class.

Invocation of a superclass constructor must be the first line in the subclass constructor.

Check here for more details

Answer 2

No,that is not a valid statement.It MUST be the first statement of the child class's constructor.

If you don't add that line,the compiler will automatically add it.

Example:

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

class B extends A {
    public B() {
       // super(); // THIS LINE WILL BE AUTOMATICALLY ADDED BY THE COMPILER.
       System.out.println("Inside B's constructor.");
       // super(); // THIS LINE WON'T COMPILE.
    }
}

public class Main {
    public static void main(String[] args) {
        B b = new B();
    }
} 

Answer 3

不，它应该是第一个语句...即使子类构造函数的第一行中没有默认构造函数，编译器也会隐式调用其父类的默认构造函数