Call a method from a constructor

[Sara Tracy]

hi !
Can I make a method call from a constructor as given below :

class Cars
{
    String password = null;
    
    Cars(String cartype) throws Exception
    {
            password = getPwd(cartype);
    }
  .......
 .........
   ...........
   private String getPwd(String car_type) throws Exception
    {
          // do some operation
    }
}

thanks
-Sara

[Campbell Ritchie]

Yes.
Constructors are there to set up the initial state of your object. So you can in theory call any method from a constructor method, but you really ought only to call methods which set up your object's initial state.

[Stan James]

Yup, that should be fine.

Do note that "this" is not assured to be good for anything until the constructor is done. Be careful not to pass "this" from the constructor to anything that needs a complete ready-to-use object.

[Sara Tracy]

Thanks Campbell and Stan !

[Campbell Ritchie]

That's a pleasure

[megha ghanekar]

Hi Sara,
U can certainly do that. But take care of following situation.

class Base
{

Base()
{
disp();
}
public void disp()
{
System.out.println("in disp of Base");
}

}

class Derived extends Base
{

Derived()
{

}
public void disp()
{
System.out.println("in disp of Derived");
}

}

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

Base b1 = new Base(); // case 1 : Base class disp called
Base b2 = new Derived(); // case 2: Derived class disp called

}
};

If there is a call to a method from constructor in Base class & if u create an object of type Base, it works fine as in case 1. But if you derive a class from such a base class & you override that method in the derived class. The derived class method will be called from Base class constructor.


Warm Regards,
meghana

[Richard Green]

private String getPwd(String car_type) throws Exception

This is just bad practise. Do something like

private String getPwd(String car_type) throws PasswordNotFoundException

instead.

where PasswordNotFoundException extends the Exception class.