Class Loaders in Java ?

• App Class Loader (System class loader)
• Extension Class Loader (Platform class loader)
• Bootstrap Class Loader

Here basically happening is when an object is created and runs in main method, a class loader comes and tries to find the Class file (it finds it in the current folder path) after finding it, the class file creates objects using class load file.

there are 3 class loaders,

• App class loader
• Extension class loader
• Bootstrap class loader

main one is bootstrap class loaders It brings other 2 class loaders ( App and exception class loader).

Reasons for class object coming to method area?

• Instance creation
• Class.forName( ) API
• Access static member

Can main method can be declared in different java types?

Answer is Yes, we can declared main method in class, Enum, Interface, Record, but cant in Annotation

In java file there should minimum initilizer methods called <clint> - Class Initialization Methods and <init> - Instance Initialization Methods

UML

UML types are used in design stages ?

Sketch – A sketch is a rough, loose diagram focusing on key design elements without full detail. It captures the main points and ideas of the system and is commonly used in industry as an early planning tool to quickly convey concepts.

Blueprint – A blueprint provides a structured overview of the system but doesn't require complete accuracy. It is more detailed than a sketch, offering a general layout of the design, though it may still be revised later in development.

Prototype – A prototype is a highly accurate and complete diagram that represents the final system design in detail. It’s crucial that every part of a prototype is correct, as it is often used in forward engineering: the design is directly implemented into a tool to create the structure and code for the system.

Illegal forward referencing rule

basically happeing is we cant assign future reference value into previous value as a example

Static int y = x; // here illegal fwd referencing error occur cuz x is initialize after the y
Static int x = 10; 

Key Points of Illegal Forward Referencing:

1. Static Variables:

   • When initializing static variables, you cannot reference another static variable declared later in the code.
   • The JVM initializes static variables in the order they are defined, so referencing a later variable results in an "illegal forward reference."

   
   static int x = y;  // Error: illegal forward reference
   static int y = 5;