The headMap() method of
SortedMap interface in Java is used to return a view of the portion of this map whose keys are strictly less than toKey.
- The map returned by this method is backed by this map, so changes in the returned map are reflected in this map, and vice-versa.
- The map returned by this method supports all optional map operations that this map supports.
Note: The map returned by this method will throw an IllegalArgumentException if any attempt is made to insert a key outside its range.
Syntax:
SortedMap<K, V> headMap(K toKey)
Where, K is the type of key maintained by this Set and V is the type of values associated with the Key.
Parameters: This function accepts a single parameter
toKey which represents high endpoint (exclusive) of the keys in the returned map.
Return Value: It returns a view of the portion of this map whose keys are strictly less than toKey.
Exception:
- ClassCastException: If the parameter toKey is not compatible with this map's comparator (or, if the map has no comparator, if toKey does not implement Comparable).
- NullPointerException: If the parameter toKey is null and this map does not permit null keys.
- IllegalArgumentException: If this map itself has a restricted range, and toKey lies outside the bounds of the range
Below programs illustrate the above method:
Program 1:
Output:
Last Key in the map is : {1=One, 2=Two}
Program 2:
