Exception Properties

Exception properties #

The information that is automatically printed on the output when the program terminates due to an exception is available as properties of exception objects as well. These properties are provided by the Throwable interface:

• .file: the source file where the exception was thrown from

• .line: the line number where the exception was thrown from

• .msg: the error message

• .info: the state of the program stack when the exception was thrown

• .next: the next collateral exception

We saw that finally blocks are executed when leaving scopes due to exceptions as well.

Collateral exception #

Naturally, code in the finally blocks can throw exceptions as well. Exceptions that are thrown while leaving scopes due to an already thrown exception are called collateral exceptions. Both the main exception and the collateral exceptions are elements of a linked list data structure, where every exception object is accessible through the .next property of the previous exception object. The value of the .next property of the last exception is null.

Example #

There are three exceptions that are thrown in the example below: the main exception that is thrown in foo() and the two collateral exceptions that are thrown in the finally blocks of foo() and bar(). The program accesses the collateral exceptions through the .next properties.

Some of the concepts that are used in this program will be explained in later chapters. For example, the continuation condition of the for loop that consists solely of exc means as long as exc is not null.