Originally posted by Hagaya Hatake: Can anyone tell my why in java if my class is MyClass then my file will be named as MyClass.java??
That's simply what Sun's compiler requires and is a pretty common convention. It is not required by the JLS, but it would be a real pain to locate the proper source file in a file-based system if the compiler didn't have those kinds of requirements.
Originally posted by Hagaya Hatake: What the class constructor really does?
Well every constructor except for Object must invoke another constructor of the same class or a constructor of it's super class. Other than that it merely executes whatever code is contained in it.
Originally posted by Hagaya Hatake: Amd how does the array subscript operator works.
By that I assume you mean an array access expression using  to access a variable of an array. Basically the int between the brackets, and it must be an int or something that can be promoted to an int, accesses the variable in the array at that index. The index starts at 0. So if I create an Object named obj of length 5 and I want to access the 5th variable then I will use obj to access the variable at index 4. I purposely call them variables because that's what they are, you are not accessing an Object, you are accessing a reference variable which either points to an Object or is null.