// Declare and Initialize the Collection Set<Integer> intSet = new HashSet<Integer>(); // Add Elements intSet.add(1); intSet.add(2); intSet.add(3); intSet.add(4); // Use the stream and collectors to get a Map out of Set System.out.println(intSet.stream().collect((Collectors.toMap(p->(Integer)p,q->((Integer)q)*500)))); // Prints {1=500, 2=1000, 3=1500, 4=2000}