Java Inconsistenties [resolved]

[Dillinger4]

I noticed some things in Java that im not sure why they are allowed. Any comments?

1.) why does a constructor allow static members to be initialized?

2.) why is a non static member able to be initialized out side
of its class constructor?

// why does a constructor allow static members to be initialized? 
// why is a non static member able to be initialized out side 
// of its class constructor?

   class Test2{
     static int x;
     static int w = 54; 
     int z = 56; 
    public Disassembler(){
      x = 73; // ?  
     
   }
  }

  public class Test1{
    public static void main(String[] args){

     Disassembler d = new Disassembler(); 
      System.out.println(Disassembler.x);
      System.out.println(Disassembler.w);
      System.out.println(d.z);
  }
}

[honeybee]

First, the code you have posted does not use a constructor, but I think that's a typo.

Second, using static variables inside a class means all objects derived from that class will share the same value for that variable. And if you want to make sure that the default/initial value of the static variable is other than zero or null, the constructor is the best place for it.

.

[Dillinger4]

Sorry, yes that was a typo.

class Disassembler{
     static int x;
     static int w = 54; 
     int z = 56; 
    public Disassembler(){
      x = 73; // ?  
     
   }
  }

  public class Test{
    public static void main(String[] args){

     Disassembler d = new Disassembler(); 
      System.out.println(Disassembler.x);
      System.out.println(Disassembler.w);
      System.out.println(d.z);
  }
}

Yes your right.
When a static variable or member (whichever you want to call it)
is declared within a class it's values are shared within all instances of the class. But declaring a static variable within a constructor wouldnt make sense because you are changing the value each time a new instance of the class is created and this defeats the concept of static variables.

[Dillinger4]

Ok i see now. I knew that a static variables value is shared among all instances. So if a static members value is changed in the class constructor it's value is changed in all instances.

I coded this real quick and it seems to show this.

[/code]
class A{
static int x;
int y;

public A(int x, int y){
this.x = x;
this.y = y;
}
}

class B extends A{
public B(int x, int y){
super(x,y);
this.x = x;
this.y = y;
}
}

class C extends A{
public C(int x, int y){
super(x,y);
this.x = x;
this.y = y;
}
}

public class Test{
public static void main(String[] args){
C c = new C(10,20); // x = 10, y = 20
System.out.println(c.x);
System.out.println(c.y);

B b = new B(30,50);
System.out.println(b.x); // x = 30 , y = 50
System.out.println(b.y);

System.out.println(c.x); // since the static variable x is changed
System.out.println(c.y); // the new value should be reflected in the class C;

}
}
[/code]

Thanks

[honeybee]

Coming to think of it, initializing a static variable right when declaring it might be another good alternative. It's the same as initializing it in the constructor.

.

[honeybee]

I think it's actually better to initialize a static variable as soon as it is declared.

Class DisAssembler
{
   static int I = 20;
   DisAssembler()
   {
   }
}

Now, load as many instances of the class as you like. The initialization has already been done, and I save on a statement in the constructor which would otherwise be executed for each object, without having any particular advantage.

.

[Dillinger4]

Hummmm. Yes maybe.