生成随机数时出现空指针异常

I have a program I need to write for a project that has been giving me a boat load of trouble. I'm writing a guessing game that allows you to try to guess a number and for you to give a number and the computer will try to guess it. My major problem is getting the computer to guess and when I try to make it guess it gives me a null pointer exception and I can't figure out how. I know it's a lot but I would be extremely grateful for any help. This is my program... (I will put ///// by the place where I get the null pointer exception)I have a program I need to write for a project