As regular readers know, we are fascinated by the bug-finding capabilities of IntelliJ IDEA. Some of the most powerful of these analysis techniques involve finding places where code lacks a necessary symmetry, indicating that piece of functionality was either half-completed, or half-removed. Variables that are written to but never read, for instance, are clear indicators that something is wrong with the code.

Other cases where symmetry is broken, which IDEA will inform you of immediately

• Interfaces and abstract classes with no implementations


• Collection variables which are queried without ever being updated, or vice versa


• Array variables which whose contents are read but never written, or vice versa


• Loops that have no exit points


• Methods that recursively call themselves, with no exit tests


• Catch clauses that do nothing but drop the caught exception


• Switch statements with no default cases, or that have a default case they don't need (for switches over enums)


• JUnit test cases which don't include any assertions

One amazing thing about these code analysis is that they can be used inline, while editing. This means that you have immediate visual feedback telling you that your aren't done yet. You don't have to wait to run a test, or even compile your code, to know that you left out some important part of your algorithm. The "Extreme Programming" folks always like to talk about the "green bar" when all your unit tests pass, and you know you're finished with the functionality you are coding. With inspections like these, you get the "green box" which tells you if your code is even internally sensible.

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