reversing keys/values - create new instance of HashMap
- by stck777
I’ve got an existing instance of HashMap simply called sale (it is Map) I use it to log customers and items history.
Is there a way to create a new instance of HashMap, that effectively reverses this usage? i.e will show each item purchased as a unique key and the corresponding value as a String set of the customers that have purchased that product. I suspect there is a simple process using keySet() in some way to iterate over the sales map but I just can’t see how to do this.
Any help would be much appreciated.