multiple String location find using a key in a tag

I want to parse an input eg: GH123FG12B1A58 .

'GH' / 'FG' / 'A' / 'B' will be there in all the tags in same order but different position . eg: GH14555523FG1555552B55551A55558

Need to find the value after every keys

I see this can be done by using patter , get start & end index ? Is there any other way to acomplish this ?