Update about and exercise introduction to match concept changes

Author: Bahaaio

concepts/exceptions/about.md

@@ -8,6 +8,8 @@ An exception is an event that occurs during the execution of a program that disr
 Exceptions are raised explicitly in Java, and the act of raising an exception is called _throwing an exception_.
 The act of handling an exception is called _catching an exception_.
 
+In Java, all exceptions are subclasses of the `Exception` class, which itself is a subclass of `Throwable`.
+
 Java distinguishes two types of exceptions:
 
 1. Checked exceptions
@@ -20,7 +22,7 @@ An example of a checked exception is the `FileNotFoundException` which occurs wh
 
 This type of exception is checked at compile-time: methods that throw checked exceptions should specify this in their method signature, and code calling a method that might throw a checked exception is required to handle it or the code will not compile.
 
-All exceptions in Java that do not inherit from `RuntimeException` are checked exceptions.
+All checked exceptions are subclasses of `Exception` that do not extend `RuntimeException`.
 
 ### Unchecked exceptions
 
@@ -29,17 +31,7 @@ An example of an unchecked exception is the `NullPointerException` which occurs
 
 This type of exception is not checked at compile-time: methods that throw unchecked exceptions are not required to specify this in their method signature, and code calling a method that might throw an unchecked exception is not required to handle it.
 
-All exceptions in Java that inherit from `RuntimeException` are unchecked exceptions.
-
-## Errors
-
-Java also has a separate category called _Errors_ which are serious problems that are external to an application.
-An example of an error is the `OutOfMemoryError` which occurs when an application is trying to use more memory than is available on the system.
-
-Like unchecked exceptions, errors are not checked at compile-time and are not usually thrown from application code.
-Unlike exceptions, Errors represent serious system-level problems that applications should generally not attempt to catch or handle.
-
-All errors in Java inherit from the `Error` class.
+All unchecked exceptions inherit from `RuntimeException`, which itself is an extension of `Exception`.
 
 ## Throwing exceptions
 
@@ -134,6 +126,17 @@ Withdrawal failed: Cannot withdraw a negative amount
 Current balance: 5.0
 ```
 
+## Errors
+
+Java also has a separate category called _Errors_ which are serious problems that are external to an application.
+An example of an error is the `OutOfMemoryError` which occurs when an application is trying to use more memory than is available on the system.
+
+Like unchecked exceptions, errors are not checked at compile-time.
+The difference is that they represent system level problems and are generally thrown by the Java Virtual machine or environment instead of the application.
+Applications should generally not attempt to catch or handle them.
+
+All errors in Java inherit from the `Error` class.
+
 ## When not to use exceptions
 
 As stated previously, exceptions are events that disrupt the normal flow of instructions, and are used to handle _exceptional events_.

exercises/concept/calculator-conundrum/.docs/introduction.md

@@ -10,6 +10,8 @@ An exception is an event that occurs during the execution of a program that disr
 Exceptions are raised explicitly in Java, and the act of raising an exception is called _throwing an exception_.
 The act of handling an exception is called _catching an exception_.
 
+In Java, all exceptions are subclasses of the `Exception` class, which itself is a subclass of `Throwable`.
+
 Java distinguishes two types of exceptions:
 
 1. Checked exceptions
@@ -22,7 +24,7 @@ An example of a checked exception is the `FileNotFoundException` which occurs wh
 
 This type of exception is checked at compile-time: methods that throw checked exceptions should specify this in their method signature, and code calling a method that might throw a checked exception is required to handle it or the code will not compile.
 
-All exceptions in Java that do not inherit from `RuntimeException` are checked exceptions.
+All checked exceptions are subclasses of `Exception` that do not extend `RuntimeException`.
 
 #### Unchecked exceptions
 
@@ -31,17 +33,7 @@ An example of an unchecked exception is the `NullPointerException` which occurs
 
 This type of exception is not checked at compile-time: methods that throw unchecked exceptions are not required to specify this in their method signature, and code calling a method that might throw an unchecked exception is not required to handle it.
 
-All exceptions in Java that inherit from `RuntimeException` are unchecked exceptions.
-
-### Errors
-
-Java also has a separate category called _Errors_ which are serious problems that are external to an application.
-An example of an error is the `OutOfMemoryError` which occurs when an application is trying to use more memory than is available on the system.
-
-Like unchecked exceptions, errors are not checked at compile-time and are not usually thrown from application code.
-Unlike exceptions, Errors represent serious system-level problems that applications should generally not attempt to catch or handle.
-
-All errors in Java inherit from the `Error` class.
+All unchecked exceptions inherit from `RuntimeException`, which itself is an extension of `Exception`.
 
 ### Throwing exceptions
 
@@ -135,3 +127,14 @@ Withdrawing -10.0
 Withdrawal failed: Cannot withdraw a negative amount
 Current balance: 5.0
 ```
+
+### Errors
+
+Java also has a separate category called _Errors_ which are serious problems that are external to an application.
+An example of an error is the `OutOfMemoryError` which occurs when an application is trying to use more memory than is available on the system.
+
+Like unchecked exceptions, errors are not checked at compile-time.
+The difference is that they represent system level problems and are generally thrown by the Java Virtual machine or environment instead of the application.
+Applications should generally not attempt to catch or handle them.
+
+All errors in Java inherit from the `Error` class.