Returns true if this map contains a mapping for the specified 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.)
Returns: true if this map contains a mapping for the specified key.
Parameters:
- key - key whose presence in this map is to be tested.
Throws:
- NullPointerException - if key is null
- ClassCastException - if key is not String
- IllegalArgumentException - if key is empty String

  Returns the value to which this map maps the specified 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.)
Returns: the value to which this map maps the specified key, or null if the map contains no mapping for this key.
Parameters:
- key - key whose associated value is to be returned.
Throws:
- NullPointerException - if key is null
- ClassCastException - if key is not String
- IllegalArgumentException - if key is empty String

  Set a named value.

  Set a named value.
Returns: The value previously associated with the given name. Returns null if no value was previously associated with the name.
Parameters:
- name - The name associated with the value.
- value - The value associated with the name.
Throws:
- NullPointerException - if the name is null.
- IllegalArgumentException - if the name is empty String.

  Adds all the mappings in a given Map to this Bindings.

  Adds all the mappings in a given Map to this Bindings.
Parameters:
- toMerge - The Map to merge with this one.
Throws:
- NullPointerException - if toMerge map is null or if some key in the map is null.
- IllegalArgumentException - if some key in the map is an empty String.

  Removes the mapping for this key from this map if it is present (optional operation).

  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.
Returns: previous value associated with specified key, or null if there was no mapping for key.
Parameters:
- key - key whose mapping is to be removed from the map.
Throws:
- NullPointerException - if key is null
- ClassCastException - if key is not String
- IllegalArgumentException - if key is empty String