Iterating through two arrays, having trouble with indices

I have a question about creating dynamic arrays and iterating through these arrays. I have a method setVoltage that takes as parameters a string and a double value. I needed some way to store these values so I created two arrays. What i need to do is iterate through the String array to see if the string parameter already exists and if it does, to set the corresponding voltage at that index. If it doesn't exist, i need to add the string device to the string array and also add the double voltage to the double array. Can someone check out my code and see what I am missing? I'm running into trouble because I want the array to realize the string is already in the array, or append it to the end of the array but I'm stuck on how to use index variables to achieve this. Thank you!I have a question about creating dynamic arrays