1  A static method can called only static field and another static method but MAIN() is also static and we can call non-static method and fields inside MAIN()?Justify it?

Misconception. A static method can call non-static methods also, but it needs an instance variable to invoke the method. Lets say if a static method could invoke a non-static method without a reference variable. In this case it woud be impossible for the compiler or the VM to resolve on which instance the method has to be invoked on, since static context is not coupled to instances.

2 How many type of modifier a class can have and what is the default modofier?

Public and package. It does not make sense to make a outer class private or protected, does it?

3 Why constructor can't be abstract or static?
If a constructor was abstract how would you create an object of it?

Well it can't be static since as I mentioned before static context is not coupled to instances and the raison d'etre of a constructor is to create instances.

4  Why a java file can't have more then one public class?

This is a small optimization technique to make the life of the compiler and the VM easier. Imagine if you could declare several
public classes within the same compilation unit(file), how difficult it would be for the poor compiler to search for it.

Java Tips by : Schizophrenicpsychosis

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