My name
is
Jon Skeet

Trying to understand statics is java, Why is it that this is the output in this code?

class Cup {
  Cup(int marker) {
    System.out.println("Cup(" + marker + ")");
  }

  void f(int marker) {
    System.out.println("f(" + marker + ")");
  }
}

class Cups {
  static Cup c1;
  static Cup c2;
  static {  
    c1 = new Cup(1);
    c2 = new Cup(2);
  }
  Cups() {
    System.out.println("Cups()");
  }
}

public class ExplicitStatic {
  static Cups x = new Cups();
  static Cups y = new Cups();

  public static void main(String[] args) {
    System.out.println("Inside main()");
  }      
}

Output:

Cup(1)
Cup(2)
Cups()
Cups()
Inside main()

So there are two static Cups, in class ExplicitStatic, why its only showing Cup(1) && Cup(2)?

The only time that new Cup() is called is within the static initializer block for Cups.

That will only be executed once, however many instances of Cups you create - indeed, even if you don't create any instances of Cups, so long as you force the Cups class to be initialized (e.g. by calling a static method on it).

If you want two Cup instances per instance of Cups then you should use instance fields instead, e.g.

class Cups {
  Cup c1 = new Cup(1);
  Cup c2 = new Cup(2);

  Cups() {
    // This will execute *after* the field initializers above
    System.out.println("Cups()");
  }
}

Then you'd get output of:

Cup(1)
Cup(2)
Cups()
Cup(1)
Cup(2)
Cups()
Inside main()

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