public boolean containsKey(Object key)
Returns true if this map contains a mapping for the specified
key. More formally, returns true if and only if
this map contains a mapping for a key k such that
(key==null ? k==null : key.equals(k)). (There can be
at most one such mapping.)

 public Object get(Object key)
Returns the value to which this map maps the specified key. Returns
null if the map contains no mapping for this key. A return
value of null does not necessarily indicate that the
map contains no mapping for the key; it's also possible that the map
explicitly maps the key to null. The containsKey
operation may be used to distinguish these two cases.

More formally, if this map contains a mapping from a key
k to a value v such that (key==null ? k==null :
key.equals(k)), then this method returns v; otherwise
it returns null. (There can be at most one such mapping.)

 public Object put(String name,
    Object value)
Set a named value.

 public  void putAll(Map toMerge)
Adds all the mappings in a given Map to this Bindings.

 public Object remove(Object key)
Removes the mapping for this key from this map if it is present
(optional operation). More formally, if this map contains a mapping
from key k to value v such that
(key==null ? k==null : key.equals(k)), that mapping
is removed. (The map can contain at most one such mapping.)

Returns the value to which the map previously associated the key, or
null if the map contained no mapping for this key. (A
null return can also indicate that the map previously
associated null with the specified key if the implementation
supports null values.) The map will not contain a mapping for
the specified key once the call returns.