Double[]coordinatestoconvert=null;
This line needs to be:
Double[] coordinatestoconvert=new Double[coordinatestoconvert.length];
You also have the same problem with coordinatesconverted.
You should also read up on the standard java style and coding conventions as it will make your code easier to read for others.
You are also doing string comparison using == rather than .equals, that is invalid.
And you will get better performance (if that matters for this program) using double rather than Double wherever you can.