Calling no argument constructor of super class

Question

If a class does not provide any constructor,the compiler will provide a default constructor,which in turn call's the no-argument of the super class. Why is this call to the no-argument constructor of the super class needed?

Answer 1

初始化该类的超级（继承）部分

Answer 2

这样您也可以初始化超类属性。

Answer 3

对于对象的构造函数仅部分构造该对象有意义吗？

Answer 4

It's part of the "is-a" relationship of subclass instances to their superclass. If a SpottedFoo is a subclass of Foo (eg each SpottedFoo "is-a" Foo ), then the Foo constructor should be called.

Otherwise, if there are initializations (private or not) performed by the Foo constructor that are skipped, there's no way a SpottedFoo can guarantee it can act like a Foo .

That's part of the contract for implementation inheritance: each subclass instance must be able to act like any other members of their superclass. This is the Liskov substitution principle.