abstract class A {
abstract void method();
}
class B extends A {
B() {
}
void method() {
}
}
class C extends B {
C() {
}
}
When I instantiate class C in main, it automatically calls the constructor for B (parent class). Is that normal or am I doing something wrong?
There is nothing wrong, there is implicit call to super constructor.
You haven't written any constructor for class C so default constructor will be provided by compiler which will be.
C(){
super();
}
If default constructor is provided, then there is a call to super().
In your case, C extends B so constructor of B gets called.
If you do not a class with any other class, then also by default it extends Object class. So Object class constructor will get called.
If a constructor body does not begin with an explicit constructor invocation and the constructor being declared is not part of the primordial class Object, then the constructor body implicitly begins with a superclass constructor invocation "super();", an invocation of the constructor of its direct superclass that takes no arguments.
http://docs.oracle.com/javase/specs/jls/se7/html/jls-8.html#jls-8.8.7
When you instantiate a C there will be constructor calls for C, B, A, and Object. A C has to be able to behave as any direct or indirect superclass, and has the fields for all of them. The job of a class X constructor is to make the object being initialized capable of working as an X.
If there is no declared constructor, the compiler creates a parameterless constructor, so every class does have at least one constructor. If a constructor that is not the Object constructor does not start with a "this" or "super" constructor call, the compiler treats it as starting with "super();", a call to a parameterless constructor for the immediate superclass.
First line of each constructor in java calls super constructor, thats how java works.
You should read about it.
