How not to comment your code

Below is a piece of code I came across recently while reviewing somebody else’s work. It is a terrific example of how not to write comments.

//Create a vector
Vector seq = new Vector();

//Count the number of items in the sequence
int count = ms.itemCount();

//Loop through the sequence getting all the values
for( int i = 0; i < count; i++ ) {
    //Convert the item to an Instance
    MInstance mi = (MInstance)ms.getAt( i );

    //Convert the instance to a HashMap
    Map data = mInstanceToMap( mi );

    //Add this to the Vector
    seq.addElement( data );
//Return the vector
return seq;

Ignoring for the minute the infuriating habit of putting spaces around parameters (doesn’t anybody read the Java style guide any more?), these comments are completely useless.

There are plenty of places to learn how to write comments. A couple of references come to mind: Steve McConnell’s “Code Complete”, “The Pragmatic Programmer”, “Programming Pearls”.

In a nutshell… don’t write comments that say what the code is doing (you can safely assume that anyone likely to need to read your comments is at least borderline literate in the progamming language in question). Maybe explain why your code is doing it, and defintely document any assumptions. Please don’t tell me new Vector() creates a new Vector…