This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
As noted above, this probably means that you are not using Java 1.5 with your IDE. However, to help you any further we need to know more information. As Igor says, it will help if you tell us what IDE and operating system you use as well as the version numbers of each.