Even for new Java developers, constructors are probably no big mystery. In essence, when you create an instance of a class, the constructor of this class is started. In the 6th part of Java Puzzlers series, we will see a case related to constructors.
public class Puzzler {
public Puzzler(){
System.out.println("Puzzler no arg constructor");
}
public static void main(String[] args){
Puzzler puzzler = new Puzzler();
}
}
In the example above Puzzler() constructor will start and "Puzzler no arg constructor" will be printed to the screen.
Now lets see a new example.
public class Puzzler {
public void Puzzler(){
System.out.println("Puzzler no arg constructor?");
}
public static void main(String[] args){
Puzzler puzzler = new Puzzler();
}
}
As you can see we added a return value to the constructor of Puzzler and you may expect that "Puzzler no arg constructor?" will get printed but this is not right. When we add a return value to the constuctor, it stops being a constructor. So it won't get started when a new instance is created.
The "return" is missing - Copy&Paste got you ;-)
ReplyDeleteNevertheless, nice puzzler, which you normally don't think about. Thank you!
Markus
Thanks Markus. By "we added a return value" I meant that we added "void" to public Puzzler. There is no real return value for none of these methods.
DeleteYou changed the constructor to a method. So the default implicit no-arg is called instead.
Delete