Increment data load in json file

i have two json file. usermaster json file contains history data, user json files contains new data. email id is unique in both files. Based on email id, i want to updated already existing data. i.e) i want to remove email id related record present in history json file and replace with record in new data json file.

I am trying to do incremental load when new data coming in, replace old data with new data.

I need java code for the task.

Help me to solve the task