Ananth,
Do you want to restrict the length (have less than n elements in the list) or the width (have n elements but display less text for the long ones) ?
If length, you can put less entries in the list in
Java. If width, you can use a CSS style to set the width of the pull down to an explicit number or pixels. Alternatively for width, you can loop through in Java, and get rid of some of the characters.
These are both technical solutions. A "better" solution would be to edit the source data to make it shorter or make a "display name" equivalent that is shorter. Sometimes chopping off data doesn't yield the best results unless a human does it.