// Make a new empty map Map<String, String> map = new HashMap<String, String>();

map.get(key) -- retrieves the stored value for a key, or null if that key is not present in the map.

map.put(key, value) -- stores a new key/value pair in the map. Overwrites any existing value for that key.

map.containsKey(key) -- returns true if the key is in the map, false otherwise.

map.remove(key) -- removes the key/value pair for this key if present. Does nothing if the key is not present.