如何生成随机字符串并为其赋值

I am making a program that has 50 questions in it,so you type the question in text field and click the button. If the question is there in the directory, then a popup will display the answer. Now i want to add a button, on which if the user clicks, the person would be able to add his question and answer in it. Adding the question is easy but I cant figure out, how to add the answer. Here's my programI am making a program that has 50 questions in