Add credits - EPI

Add credits  AddingCredits.java

  public static class ClientsCreditsInfo {
    private int offset = 0;
    private Map<String, Integer> credits = new HashMap<>();
    private TreeMap<Integer, Set<String>> inverseCredits = new TreeMap<>();

    public boolean insert(String s, int c) {
      if (!credits.containsKey(s)) {
        credits.put(s, c - offset);
        Set<String> set = inverseCredits.get(c - offset);
        if (set == null) {
          set = new HashSet<>();
          inverseCredits.put(c - offset, set);
        }
        set.add(s);
        return true;
      }
      return false;
    }

    public boolean remove(String s) {
      Integer creditsIt = credits.get(s);
      if (creditsIt != null) {
        inverseCredits.get(creditsIt).remove(s);
        if (inverseCredits.get(creditsIt).isEmpty()) {
          inverseCredits.remove(creditsIt);
        }
        credits.remove(s);
        return true;
      }
      return false;
    }

    public int lookup(String s) {
      Integer it = credits.get(s);
      return it == null ? -1 : it + offset;
    }

    public void addAll(int C) {
      offset += C;
    }

    public String max() {
      return inverseCredits.isEmpty() ? "" : inverseCredits.lastEntry()
          .getValue().iterator().next();
    }
  }