// Hash Table: using String keys, with the java String method hashCode()
import java.util.*;

interface Map {
   public int size();
   public boolean isEmpty();
   public Object get(String k);
   public Object put(String k, Object v);
   public Object remove(String k);
}

class Pair {
   public String key;
   public Object value;

   Pair(String k, Object v) {
      key = k;
      value = v;
   }
}

class ChainedHashTable implements Map {
   int size;
   int capacity;
   Vector bucket[];

   ChainedHashTable() { this(1000); }
   ChainedHashTable(int cap) {
      capacity = cap;
      bucket = new Vector[cap];
      size = 0;
      for (int i = 0; i < cap; i++) 
         bucket[i] = null;
   }
   public int size() { return size; }
   public boolean isEmpty() { return size == 0; }
   public Object get(String k){
      int h = k.hashCode() % capacity;
      if (bucket[h] != null) {
         for (int i = 0; i < bucket[h].size(); i++) {
            Pair p = (Pair) bucket[h].get(i);
            if (p.key.equals(k)) return p.value;
         }
      }
      return null;
   }
   public Object put(String k, Object v) {
      int h = k.hashCode() % capacity;
      if (bucket[h] == null) bucket[h] = new Vector();
      for (int i = 0; i < bucket[h].size(); i++) {
         Pair p = (Pair) bucket[h].get(i);
         if (p.key.equals(k)) {
            Object answer = p.value;
            p.value = v;
            return answer;
         }
      }
      bucket[h].add(new Pair(k, v));
      size ++;
      return null;
   }
   public Object remove(String k) {
      int h = k.hashCode() % capacity;
      if (bucket[h] != null) {
         for (int i = 0; i < bucket[h].size(); i++) {
            Pair p = (Pair) bucket[h].get(i);
            if (p.key.equals(k)) {
               bucket[h].remove(i);
               size --;
               return p.value;
            }
         }
      }
      return null;
   }

   public void dump() {
      for (int i = 0; i < capacity; i++) {
         if (bucket[i] != null) {
            System.out.print("" + i + ": ");
            for (int j = 0; j < bucket[i].size(); j++) {
                Pair p = (Pair) bucket[i].get(j);
                System.out.print("(" + p.key + " " + p.value + ") ");
            }
            System.out.println();
         }
      }
   }
   public static void main(String args[]) {
      Map m = new ChainedHashTable(4);
      testMap(m);
   }
   public static void testMap(Map m) {
      boolean done = false;
      while (!done) {
         try {
           Scanner sc = new Scanner(System.in);
           System.out.println("\ncmds are + - D F Q: >>");
           String cmd = sc.next();
           String key = null;
           String value = null;
           char command = cmd.charAt(0);
           if (command != 'Q' && command != 'D') key = sc.next();
           if (command == '+') value = sc.next();
           switch (cmd.charAt(0)) {
              case 'Q': done = true; value = null; break; 
              case 'D': value = null; ((ChainedHashTable) m).dump(); break; 
              case '+': value = (String) m.put(key, value); break;
              case '-': value = (String) m.remove(key); break;
              case 'F': value = (String) m.get(key); break;
           }
           if (value != null) System.out.println("Value: " + value);
        } catch (Exception e) {
           System.out.println("Error " + e.toString());
        }
      }   
   }
}