Checking Java Programs

Source Code Checking with PMD

PMD is a Java source code checker which reads the Java source code in your project looking for patterns that indicate errors or suboptimal practices. Because it reads the source code, it can find stylistic omissions that other tools like FindBugs cannot, such as leaving off parenthesis around the body of an if statement:

if (a < 0)
      System.err.printf("Value of 'a' is %d but may not be negative%n", a);

There is nothing functionally wrong with this code, but it's bad style. Sun's Java Coding Style document (http://java.sun.com/docs/codeconv) says to always use curly braces around the body of an if statement or a loop. And sure enough, somebody is going to come along and, under time pressure, insert an additional debugging printout betwixt the if and the printf, assuming from their indentation that the new statement and the printf will both be controlled by the if. Java isn't Python, so that doesn't work, and the program will fail, printing the diagnostic even when the datum being tested is valid. But if you use PMD, you'll know it's a problem long before it gets into production.

The PMD project offers a very large set of rules, and we'll only cover a few of them here. The project maintains a complete list (http://pmd.sourceforge.net/rules/index.html) of almost 220 rules in almost 30 categories; a copy is also included in the documentation that ships with PMD. Each rule has a name, a short description that shows up by default, and a longer explanation that ...