INHERITANCE AND POLYMORPHISM - Introduction to Java Programming - page 415

The syntax to call a superclass's constructor is:

super (), or super (parameters);

The statement super() invokes the no-arg constructor of its superclass, and the statement
super(arguments) invokes the superclass constructor that matches the arguments . The
statement super() or super(arguments) must appear in the first line of the subclass's
constructor; this is the only way to explicitly invoke a superclass constructor. For example, the
constructor in lines 12-17 in Listing 11.2 can be replaced by the following code:

public CircleFromSimpleGeometricObject(
double radius, String color, boolean filled) {
super (color, filled);
this .radius = radius;

}

Caution
You must use the keyword super to call the superclass constructor, and the call must
be the first statement in the constructor. Invoking a superclass constructor's name in a
subclass causes a syntax error.

11.3.2 Constructor Chaining
A constructor may invoke an overloaded constructor or its superclass constructor. If neither is
invoked explicitly, the compiler automatically puts super() as the first statement in the con-
structor. For example:

public ClassName() {
// some statements

public ClassName() {

super ();

Equivalent

// some statements

}

}

public ClassName( double d) {
// some statements

public ClassName( double d) {

super ();

Equivalent

// some statements

}

}

In any case, constructing an instance of a class invokes the constructors of all the superclasses
along the inheritance chain. When constructing an object of a subclass, the subclass construc-
tor first invokes its superclass constructor before performing its own tasks. If the superclass is
derived from another class, the superclass constructor invokes its parent-class constructor
before performing its own tasks. This process continues until the last constructor along the
inheritance hierarchy is called. This is called constructor chaining .
Consider the following code:

constructor chaining

1 public class Faculty extends Employee {

2 public static void main(String[] args) {

3
4 }
5
6

new Faculty();

public Faculty() {