The rarest method accepts a map with string keys and integer values, representing people's names mapped to their ages. It returns the integer value (age) that occurs least frequently in the map. If there is a tie, it returns the younger age. If the map is empty, it throws an exception. The example map shows three people aged 20, two aged 22, and four aged 25. So the method would return 22. If another person aged 22 was added, creating a tie between ages 20 and 22, it would return 20 since that is the younger age.