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.
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That is a common mistake. You are trying to contact something from a static method, possibly the main method. You should consider whether you are right working in a static context in the first place. Then, you need to create an object reference and call methods on that.