More formally, if this map contains a mapping from a key - * {@code k} to a value {@code v} such that {@code (key==null ? k==null : - * key.equals(k))}, then this method returns {@code v}; otherwise - * it returns {@code null}. (There can be at most one such mapping.) - * - *
If this map permits null values, then a return value of
- * {@code 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 {@code null}. The {@link #containsKey
- * containsKey} operation may be used to distinguish these two cases.
- *
- * @param key the key whose associated value is to be returned
- * @return the value to which the specified key is mapped, or
- * {@code null} if this map contains no mapping for the key
- * @throws ClassCastException if the key is of an inappropriate type for
- * this map
- * (optional)
- * @throws NullPointerException if the specified key is null and this map
- * does not permit null keys
- * (optional)
- */
- @Override
- public Object get(Object key) {
- return attrs.get(key);
- }
-
- /**
- * Associates the specified value with the specified key in this map
- * (optional operation). If the map previously contained a mapping for
- * the key, the old value is replaced by the specified value. (A map
- * m is said to contain a mapping for a key k if and only
- * if {@link #containsKey(Object) m.containsKey(k)} would return
- * true.)
- *
- * @param key key with which the specified value is to be associated
- * @param value value to be associated with the specified key
- * @return the previous value associated with key, or
- * null if there was no mapping for key.
- * (A null return can also indicate that the map
- * previously associated null with key,
- * if the implementation supports null values.)
- * @throws UnsupportedOperationException if the put operation
- * is not supported by this map
- * @throws ClassCastException if the class of the specified key or value
- * prevents it from being stored in this map
- * @throws NullPointerException if the specified key or value is null
- * and this map does not permit null keys or values
- * @throws IllegalArgumentException if some property of the specified key
- * or value prevents it from being stored in this map
- */
- @Override
- public Object put(String key, Object value) {
- return attrs.put(key, value);
- }
-
- /**
- * Removes the mapping for a 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 this map previously associated the key, - * or null if the map contained no mapping for the key. - * - *
If this map permits null values, then a return value of - * null does not necessarily indicate that the map - * contained no mapping for the key; it's also possible that the map - * explicitly mapped the key to null. - * - *
The map will not contain a mapping for the specified key once the
- * call returns.
- *
- * @param key key whose mapping is to be removed from the map
- * @return the previous value associated with key, or
- * null if there was no mapping for key.
- * @throws UnsupportedOperationException if the remove operation
- * is not supported by this map
- * @throws ClassCastException if the key is of an inappropriate type for
- * this map
- * (optional)
- * @throws NullPointerException if the specified key is null and this
- * map does not permit null keys
- * (optional)
- */
- @Override
- public Object remove(Object key) {
- return attrs.remove(key);
- }
-
- /**
- * Copies all of the mappings from the specified map to this map
- * (optional operation). The effect of this call is equivalent to that
- * of calling {@link #put(Object, Object) put(k, v)} on this map once
- * for each mapping from key k to value v in the
- * specified map. The behavior of this operation is undefined if the
- * specified map is modified while the operation is in progress.
- *
- * @param m mappings to be stored in this map
- * @throws UnsupportedOperationException if the putAll operation
- * is not supported by this map
- * @throws ClassCastException if the class of a key or value in the
- * specified map prevents it from being stored in this map
- * @throws NullPointerException if the specified map is null, or if
- * this map does not permit null keys or values, and the
- * specified map contains null keys or values
- * @throws IllegalArgumentException if some property of a key or value in
- * the specified map prevents it from being stored in this map
- */
- @Override
- public void putAll(Map m) {
- attrs.putAll(m);
- }
-
- /**
- * Removes all of the mappings from this map (optional operation).
- * The map will be empty after this call returns.
- *
- * @throws UnsupportedOperationException if the clear operation
- * is not supported by this map
- */
- @Override
- public void clear() {
- attrs.clear();
- }
-
- /**
- * Returns a {@link Set} view of the keys contained in this map.
- * The set is backed by the map, so changes to the map are
- * reflected in the set, and vice-versa. If the map is modified
- * while an iteration over the set is in progress (except through
- * the iterator's own remove operation), the results of
- * the iteration are undefined. The set supports element removal,
- * which removes the corresponding mapping from the map, via the
- * Iterator.remove, Set.remove,
- * removeAll, retainAll, and clear
- * operations. It does not support the add or addAll
- * operations.
- *
- * @return a set view of the keys contained in this map
- */
- @Override
- public Set