Subversion Repositories programming

public interface Map {
  public Object get(Object key);
  // RETURN: value;
  // POST: if value!=null, then (key,value) is in this map;
  //       if value==null, then no record in this map has the given key;
  public Object put(Object key, Object value);
  // RETURN: oldValue;
  // POST: if oldValue==null, then (key,value) is in this map;
  //       if oldValue!=null, then (key,oldValue) was in this map;
  public Object remove(Object key);
  // RETURN: oldValue;
  // POST: if oldValue==null, no record in this map has the given key;
  //       if oldValue!=null, then (key,oldValue) was in this map;
  public int size();
  // RETURN: n;
  // POST: this map contains n records;
}