abstract classes

[Maria Garcia]

how are the constructors of abstract classes declared, public or private ?

[Valentin Crettaz]

rejinky,
Welcome to Javaranch
We'd like you to read the Javaranch Naming Policy and change your publicly displayed name to comply with our unique rule. Thank you.
As for your question, it doesn't matter what the accessibility of the constructors of the abstract class are. They may be public, protected, "default" or private, the bottom line is that at least one of them must be accessible for the subclass to invoke. The compiler won't allow you to invoke any constructor of an abstract class from outside a subclass of that abstract class.

[Maria Garcia]

thank you Valentin for that immediate reply.
FYI, I already changed my Displayed Name.

[Valentin Crettaz]

FYI, I already changed my Displayed Name
Thank you very much

[Snigdha Solanki]

Valentin,
I get the following error when trying to compile superclass.
javac -classpath %CLASSPATH%;.\ b.java
b.java:3: a() has private access in a
public b(int t){
^
1 error

 
abstract class a{
private a(){
}
}
 

 
class b extends a{
public b(int t){
}
}
 

It works fine if I declare the constructor of a as public or protected.

[Valentin Crettaz]

Snigdha,
That's exactly what I mentioned above:
the bottom line is that at least one of them must be accessible for the subclass to invoke.
If the constructor of class a is declared private, there is no constructor in class a for class b to access, thus the compilation error.
The following code is perfectly legal:

abstract class a{
   private a(){}
   protected a(int i){
      this();
   }
   protected a(int t,int s){
      this();
   }
} 
class b extends a{
   public b(int t){
      super(t);
   }
}

Note that although there is a private constructor (which is used by the protected ones), the code compiles because there are other accessible constructors (the 2nd and 3rd). That's what I meant actually. Sorry if that wasn't clear

[Snigdha Solanki]

Thanks It's clear now.