Exception handling: dealing with errors

Bruce Eckel's Thinking in Java Contents | Prev | Next

dealing with errors

Ever since the beginning of programming languages, error handling has been one of the most difficult issues. Because it’s so hard to design a good error-handling scheme, many languages simply ignore the issue, passing the problem on to library designers who come up with halfway measures that can work in many situations but can easily be circumvented, generally by just ignoring them. A major problem with most error-handling schemes is that they rely on programmer vigilance in following an agreed-upon convention that is not enforced by the language. If the programmer is not vigilant, which is often if they are in a hurry, these schemes can easily be forgotten.

Exception handling wires error handling directly into the programming language and sometimes even the operating system. An exception is an object that is “thrown” from the site of the error and can be “caught” by an appropriate exception handler designed to handle that particular type of error. It’s as if exception handling is a different, parallel path of execution that can be taken when things go wrong. And because it uses a separate execution path, it doesn’t need to interfere with your normally-executing code. This makes that code simpler to write since you aren’t constantly forced to check for errors. In addition, a thrown exception is unlike an error value that’s returned from a function or a flag that’s set by a function in order to indicate an error condition, These can be ignored. An exception cannot be ignored so it’s guaranteed to be dealt with at some point. Finally, exceptions provide a way to reliably recover from a bad situation. Instead of just exiting you are often able to set things right and restore the execution of a program, which produces much more robust programs.

Java’s exception handling stands out among programming languages, because in Java, exception-handling was wired in from the beginning and you’re forced to use it. If you don’t write your code to properly handle exceptions, you’ll get a compile-time error message. This guaranteed consistency makes error-handling much easier.

It’s worth noting that exception handling isn’t an object-oriented feature, although in object-oriented languages the exception is normally represented with an object. Exception handling existed before object-oriented languages.



Comments

  • There are no comments yet. Be the first to comment!

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • This paper introduces IBM Java on the IBM PowerLinux 7R2 server and describes IBM's implementation of the Java platform, which includes IBM's Java Virtual Machine and development toolkit.

  • Not all enterprise applications are created equal. Sophisticated applications need developer support but other more basic apps do not. With the right tools, everyone is a potential app developer with ideas and a perspective to share. Trends such as low-code development and model driven development are fundamentally changing how and who creates applications. Is your organization ready? Read this report and learn: The seven personas of enterprise app delivery How application ownership is spreading to the …

Most Popular Programming Stories

More for Developers

Latest Developer Headlines

RSS Feeds