I have a question

please this is just theory at the moment I am a novice java programmer

Is it possible for me to write information to a hashmap and then once it has
been written to extract a certain piece of information in that hash map and
store it in a variable

then manipulate the information stored in the variable and then put the
information from the variable back into the hashmap in the place that i got
it from

basically I have to be able to have something like this in the hasmap

Product1          ProductName          10

I want to take the 10 store it in a variable

then decrement the variable and store the variable back in the hasmap so the
hasmap looks like this

Product1          ProductName          9

please dont scare me with some complicated stuff just a hint in the right
direction would be good

Thanks in advance

Christo