Obsolete vs. deprecated in software development

The key difference between a deprecated component and an obsolete one is that a deprecated component is fully functional but scheduled to be phased out, while an obsolete item has been fully phased out and cannot be used in a modern environment.

What is a deprecated method?

In software development, it is common for components to be listed as deprecated. If a feature or function is deprecated, developers are warned that support for that feature will be withdrawn in the near future. When support is withdrawn, old code will no longer work on new releases, forcing developers to rewrite, retest, and reintegrate it into their codebase.

Forward-thinking developers avoid using deprecated classes, methods, and functions. This shouldn’t be hard, as documentation typically points to preferred ways to achieve the same functionality when deprecation occurs.

What does it mean to be obsolete?

Something that is obsolete has completely lost its usefulness. In software development, a resource that has been made obsolete can no longer be used, and attempts to use it will result in either a runtime or compile-time error.

More generally, an item may become obsolete when its use is dangerous, it has well-known security flaws, it is no longer produced, or it has been replaced by something significantly better.

Examples of Obsolete and Deprecated Items
Obsolete Items Deprecated Items
Adobe Flash Player Thread.stop() in Java
Windows 3.1 HTML’s <marquee> tag
Google+ Date.getYear() in Java
Java Applets UIWebView in iOS
Floppy Disks System.runFinalizersOnExit() in Java

In summary, avoid using deprecated components, as they are being phased out, while an item that is obsolete has been complete phased out and can’t be used.