An easy way to explain "Calling constructors from constructors"

[Kamal Ahmed]

Hi,



I have just finished modifying Bruce Eckel's code to understand how "Calling constructors from constructors" work, so here it is, Enjoy

 public class Flower {
private int petalCount = 0;
private String s = new String("null");
Flower(int petals) {
petalCount = petals;
System.out.println("Flower(int petals) "
+ petalCount);
}
Flower(String ss) {
System.out.println("Flower(String ss) " + ss);
s = ss;
}
Flower(String s, int petals) {
this(s);// Can't call two!
//this(petals);
this.s = s; // Another use of "this"
System.out.println("Flower(String s, int petals)");
}
Flower() {
this("hi", 47);
System.out.println("Flower() ");
}
void print() {
// ! this(11); // Not inside non-constructor!
System.out.println("petalCount = " + petalCount + " s = " + s);
}
public static void main(String[] args) {
Flower x = new Flower();
x.print();
}
} 

Now as you notice:



1. In the constructor, Flower(String s, int petals), if this(s); is used, then it basicaly calls Flower(String ss), and

System.out.println("Flower(String ss) " + ss); is printed



2. If the constructor, Flower(String s, int petals), this(petals); is used, then Flower(int petals) is called, and

System.out.println("Flower(int petals) "
+ petalCount); 

is printed



3. Also we cannot have 2 this() in the same constructor



4. In print( ) you can see that the compiler won�t let you call a constructor from inside any method other than a constructor.



Hope this is helpful.

Thanks,

-Kamal.

[Jeff Albertson]

Does Bruce Eckel really write new String("null")?

[marc weber]

 

Originally posted by Jeff Albertson:
Does Bruce Eckel really write new String("null")?

Curiously, he does. :roll: