A call to super() is the first statement inserted by default in all the constructors of all the classes. A class which does not have a super class, actually has a super class called Object. A call to super() means calling the default constructor of the super class. This is necessary because before initializing a class the super class should be initialized. A user can also call a parametric constructor from a constructor eg: super(1). Note here super(1) should be the first statement in the constructor.
The this() call is a call to a constructor of the same class. This also should be the first statement in the constructor. If this statement occurs in a constructor then the call to super() is omitted.
Below examples explains their working.
public class Animal {
public Animal(){
System.out.println("Animal constructur called");
}
}
public class Dog extends Animal{
public Dog(int i){
this();
System.out.println("Dog constructur called");
}
public Dog(){
System.out.println("Dog deault constructur called");
}
}
public class Test {
public static void main(String[] args) {
Dog dog = new Dog(1);
}
}
Animal constructur called Dog deault constructur called Dog constructur called
public class Animal {
public Animal(int i){
System.out.println("Animal constructur called");
}
}
public class Dog extends Animal{
public Dog(int i){
this();
System.out.println("Dog constructur called");
}
public Dog(){
super(1);
System.out.println("Dog deault constructur called");
}
}
