Using FindBugs in Tooltwist

FindBugs is an eclipse plugin that reviews code and checks for common java coding errors.  The errors range from un-removed "TODO" comments; to inefficiency in the code; to possible masking of potential bugs.

To install FindBugs:

1. Click on Help > Install New Software...
2. Click on Add...
3. Fill in the following:
    - Name: FindBugs
    - Location: http://findbugs.cs.umd.edu/eclipse/
4. Check FindBugs and the packages underneath it
5. Continue the installation process by clicking on Next, I Agree, etc..

To use FindBugs

1. Right-Click on the project
2. Select Find Bugs > Find Bugs
3. The Find Bugs perspective gives a list of possible bugs with suggestions

Here's a list of common bugs found by Find Bugs on the Tutuki project and suggested actions:

1. When concatinating strings, especially within a loop, use StringBuffer instead of String
    wrong way:

        String s = "----\n";
        for (int i = 0; i < 10; i++) {
            s += "hello\n";
        }
        System.out.println(s);

    correct way:

        StringBuffer s = new StringBuffer("----\n");
        for (int i = 0; i < 10; i++) {
            s.append("hello\n");
        }
        System.out.println(s.toString());

    note: StringBuffer does not override the equals(Object) method.  Use the equals method of String by:

        StringBuffer sb = new StringBuffer("hello");
        if ("hello".equals(sb.toString())) ...

    or:

        if (sb.toString().equals("hello")) ...

2. Avoid empty catch blocks
    wrong way:

        catch (Exception ex) {}

    note: at the very least, do an ex.printStackTrace();  This is still not recommended though.  Best is to re-raise an exception.  Let tooltwist/tomcat/java handle that for you.
    best way:

        catch (Exception ex) {
            // few handling/logging statements
            throw new CustomException(ex);
        }

3. Handle specific exceptions explicitly.
    wrong way:

        catch (Exception ex)

    right way:

        catch (ExType1 ex) {
            ...
        }
        catch (ExType2 ex) {
            ...
        }

    According to FindBugs: "this construct also accidentally catches RuntimeException as well, masking potential bugs."

4. When a variable is not in use, delete it.  If you think the code will use this later, just comment it out.  The bulk of the errors/warnings was because of advance code.  One particular sample is the log4j logger.

5. Misc:
    - Always remove autogenerated comments.  These are comments marked with the text 'TODO Auto-generated'.
    - Always remove unused imports.  An eclipse shortcut is to press Command-Shift-'O' to organize imports.