This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
You're using a Java 5 compiler, and Java 5 has generics. Basically, Java now lets you specify what kind of objects that LinkedList can hold, and the warning is telling you that you're not taking advantage of that feature. Read the article for more info.
By the way, I deleted a copy of this message from the Java in General (Intermediate) forum. For an explanation, please read this.