列表排序时在List中查找值的最佳方法

Let's say I have a Java ArrayList, that is sorted. Now I would like to find the index of value x. What would be the fastest (without more than 30 lines of code) way to do this? Use of the IndexOf() method? Iterate through all values in a simple for loop? Use of some cool algorithm? We are talking about around let's say 50 integer keys.Let's say I have a Java ArrayList, that is sort