Can you explain the functional role and features of initialization blocks in Java?

In Java and the hierarchy of exceptions, the base class is java.lang.Throwable, which has two main subclasses:

• Error — errors that are usually not handled by applications (e.g., OutOfMemoryError).
• Exception — exceptions that can and should be handled.

Exception is further divided into:

• Checked exceptions — require explicit handling or declaration (IOException, SQLException).
• Unchecked exceptions — subclasses of RuntimeException, do not require handling (NullPointerException, IllegalArgumentException).

The structure looks like this:

Throwable
├── Error
└── Exception
    ├── RuntimeException (unchecked)
    └── Other exceptions (checked)

This allows the compiler and developers to understand which exceptions need explicit handling and which do not.