Returns <tt>true</tt> if this map contains a mapping for the specified
key. More formally, returns <tt>true</tt> if and only if
this map contains a mapping for a key <tt>k</tt> such that
<tt>(key==null ? k==null : key.equals(k))</tt>. (There can be
at most one such mapping.)
@param key key whose presence in this map is to be tested
@return <tt>true</tt> if this map contains a mapping for the specified
key
@throws ClassCastException if the key is of an inappropriate type for
this map
(<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
@throws NullPointerException if the specified key is null and this map
does not permit null keys
(<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
Returns <tt>true</tt> if this map contains a mapping for the specified key. More formally, returns <tt>true</tt> if and only if this map contains a mapping for a key <tt>k</tt> such that <tt>(key==null ? k==null : key.equals(k))</tt>. (There can be at most one such mapping.)
@param key key whose presence in this map is to be tested @return <tt>true</tt> if this map contains a mapping for the specified key @throws ClassCastException if the key is of an inappropriate type for this map (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>) @throws NullPointerException if the specified key is null and this map does not permit null keys (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)