Tell me about the exception hierarchy in Java, checked and unchecked exceptions

In Java, the exception hierarchy starts with the class java.lang.Throwable, which has two main subclasses: Error and Exception.

• Error — errors that are usually not handled by the application (e.g., OutOfMemoryError). They indicate serious problems in the JVM.

• Exception — exceptions that can be handled by the program. Exceptions are divided into:

  1. Checked exceptions — inherit from Exception, but not from RuntimeException. The compiler requires these exceptions to be either caught in a try-catch block or declared in the method signature with throws. Examples: IOException, SQLException.

  2. Unchecked exceptions — inherit from RuntimeException. The compiler does not require mandatory handling or declaration of these exceptions. They usually arise from programming errors, such as NullPointerException, IllegalArgumentException.

Example:

try {
    // code that may throw IOException
} catch (IOException e) {
    e.printStackTrace();
}

// Unchecked exception can be not handled
int a = 5 / 0; // ArithmeticException

Thus, checked exceptions are intended for situations that can and should be handled, while unchecked exceptions are for errors that usually indicate bugs in the code.