Enthuware

import java.*; //1
public abstract class InternalLogic //2
{    
float density = 20.0; //3    
public class Doer //4   
  {       
void do() //5       
{          //lot of valid code.      
  }   
  }
}
I just wanted to know whether the import statement on line 1 is correct since it has just classname?

Thanks in advance!

Yes, the import statement is correct although it is redundant because there is no class in java package.

I thought you could only have one public class in a file. Are abstract classes an exception to that rule?

If so, is the only allowed filename for this java file then 'Doer.java' ??



/// nevermind: code experimentation led me to the following: there can only be one public class in a file, but a class can have as much public INNER classes as desired.

Line 3: float density = 20.0;

I thought when you are assigning a constant, there is automatic casting?

vchhang wrote:Line 3: float density = 20.0;

I thought when you are assigning a constant, there is automatic casting?

But not with float, double, or long.

HTH,
Paul.

It appears that I have to read the JLS because no books have all of these information.

Hi,

Can you please clear my doubt as to why float density = 20.0; is not acceptable by compiler??

I am completely lost here.

It is invalid because 20.0 is a double. You can't assign a double to a float variable without a cast because double is a bigger data type than float. Even though the number 20.0 can fit into a float, java language designers have disallowed assignment of double to float or long to int without an explicit cast.

I guess now i get it..the default data type for integers is double and not float and so if i have to declare a float I need to declare it with F or f at end...correct??

abhishek2204 wrote:the default data type for integers is double and not float and so if i have to declare a float I need to declare it with F or f at end...correct??

No, default data type for integers is int. 20.0 is not an integer. 20 is an integer. 20.0 is a floating point number and it is considered a double in java. 20.0f or 20.0F is float.

Sorry I misquoted... I meant that default type for decimals is double and not float and to declare a float you will need to postfix f or F...