我如何比较java中的两个字符串，并定义哪个字符串比另一个字符串更小?

I want to use the binary search algorithm to search the string which has been entered by the user in a very big sorted file. I can not compare the string which has been entered by the user with the string which has been located in the middle line of the file to continue my binary search.I want to use the binary search algorithm to se