Question

List various exceptional conditions that have occurred throughout this text. List as many additional exceptional conditions as you can. For each of these exceptions, describe briefly how a program typically would handle the exception, using the exception-handling techniques discussed in this chapter. Some typical exceptions are division by zero, arithmetic overflow, array subscript out of bounds, exhaustion of the free store, etc.

Short answer

To manage exceptions like division by zero, overflow, out-of-bounds errors, and memory exhaustion, use try-catch blocks to handle errors gracefully.

Step-by-step solution

Identify Division by Zero Exception

Division by zero is an arithmetic operation where a number is divided by zero, resulting in an undefined value. In a programming context, dividing a number by zero typically results in a runtime error. To handle this exception, many programs use a try-catch block where the division operation is wrapped in a try block, and any division by zero is caught in the catch block. The program can then display an error message or assign a default value.

Tackle Arithmetic Overflow Exception

Arithmetic overflow occurs when a calculation exceeds the maximum value a variable can store. To handle overflow, most programming languages offer specific exceptions that can be caught, such as an `OverflowException` in C#. The program can attempt to handle overflow by using larger data types or by encapsulating the arithmetic operation in a try-catch block and providing a meaningful error message.

Manage Array Subscript Out of Bounds

An array subscript out of bounds occurs when a program tries to access an array element with an index greater than the array's size. To handle this exception, you can use bounds-checking methods provided by the language or manually check if an index is within the valid range before accessing the array. If an invalid index is detected, a try-catch block can be used to catch the exception and handle it appropriately.

Resolve Exhaustion of Free Store (Memory)

Memory exhaustion happens when a program tries to allocate more memory than is available in the free store. To handle this situation, most languages allow catching this exception using specific constructs like a `bad_alloc` exception in C++ or an `OutOfMemoryError` in Java. Upon catching the exception, the program can free unnecessary resources or prompt the user to close other applications to free memory.

Detect Input/Output Exceptions

Input/Output exceptions occur during file operations, such as when a file that the program tries to read does not exist. A program can handle such exceptions by using try-catch blocks to catch any IO-related exceptions. Once caught, the program may retry the operation, ask the user for a new file path, or log an error message for further action.

Key concepts

Division by Zero

Division by zero occurs when you attempt to divide a number by zero, which is mathematically undefined. In programming, this often results in a runtime error that can cause your program to crash. To prevent this, programmers typically use exception handling techniques like try-catch blocks.

Within a try-catch block, the operation that might lead to division by zero is placed inside the 'try' block. If the operation attempts to divide by zero, the 'catch' block is triggered.

• The 'catch' block can handle the error by displaying an error message to the user, which explains what went wrong.
• An alternative might be to set a default return value and allow the program to continue executing safely.

It's important to always validate inputs where division is involved to avoid division by zero at the source. This can mean checking for zero in the divisor and deciding on an appropriate action, such as prompting the user to enter a new number.

Arithmetic Overflow

Arithmetic overflow happens when a calculation produces a result that exceeds the storage capacity of the data type intended to hold it. For instance, adding two large integers may result in a value that cannot be stored in an int variable.

To handle arithmetic overflow, several strategies are possible:

• Use larger data types that can store bigger numbers. For example, using a long instead of an int.
• Implement exception handling through try-catch blocks, specifically catching an ``OverflowException`` in languages like C#.
• In some cases, set or log an overflow flag that can be checked elsewhere in the program to adjust for the overflow condition.

These prevention techniques help maintain the stability of the program by politely managing any unintended large-scale results.

Array Subscript Out of Bounds

An "array subscript out of bounds" error occurs when you try to access an index in an array that does not exist. For example, if an array has ten elements, trying to access the 11th element will trigger this error. This can lead to unpredictable behavior in your program.

To avoid such problems, programmers often use:

• Bounds-checking methods provided by programming languages, which automatically validate index values.
• Manual checks to ensure the index is within valid bounds before accessing the array.

Using these techniques, a program can prevent illegal index access and thus avert potential runtime errors. If an out-of-bounds index is detected, it can be caught in a try-catch block, which can then log a warning and prevent the program from crashing.

Memory Management

Effective memory management is critical to ensure efficient and stable software. Problems such as memory leaks or exhaustion of available memory can lead to crashes or poor performance. Memory exhaustion occurs when a program tries to allocate more memory than is available in system resources.

To handle memory-related exceptions, developers should:

• Use exception handling like C++'s `bad_alloc` to manage situations where memory cannot be allocated.
• Free unused resources where possible, thereby ensuring that memory is available when needed.
• Encourage user actions to close unused applications to free up additional memory, especially in resource-constrained environments.

By employing these techniques, programs can maintain efficiency and gracefully handle cases where memory is limited.