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SortedMap subMap() method in Java

Last Updated : 26 Nov, 2018
The subMap() method of SortedMap interface in Java is used to return a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive.
  • 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 an attempt is made to insert a key outside its range. Syntax:
SortedMap<K, V> subMap(K fromKey,
 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 two parameter fromKey and toKey which represents low endpoint (inclusive) and high endpoint (exclusive) respectively of the keys in the returned map. Return Value: It returns a view of the portion of this map whose keys range from fromKey to toKey. Exception:
  • ClassCastException: If the parameter fromKey is not compatible with this map's comparator (or, if the map has no comparator, if fromKey does not implement Comparable).
  • NullPointerException: If the parameter fromKey is null and this map does not permit null keys.
  • IllegalArgumentException: If this map itself has a restricted range, and fromKey lies outside the bounds of the range
Below programs illustrate the above method: Program 1:
Output:
Elements in range from 2 to 5 in the map is : {2=Two, 3=Three, 4=Four}
Program 2:
Output:
Key in range from D to Z in the map is : {Five=It, Four=Code, One=Geeks, Three=Geeks, Two=For}
Reference: https://docs.oracle.com/javase/10/docs/api/java/util/SortedMap.html#subMap(K)
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