SortedMap Interface in Java with Examples

SortedMap is an interface in collection framework. This interface extends Map inrerface and provides a total ordering of its elements (elements can be traversed in sorted order of keys). Exampled class that implements this interface is TreeMap.

The main characteristic of a SortedMap is that, it orders the keys by their natural ordering, or by a specified comparator. So consider using a TreeMap when you want a map that satisfies the following criteria:

• null key or null value are not permitted.
• The keys are sorted either by natural ordering or by a specified comparator.

Methods of SortedMap:

1. subMap(K fromKey, K toKey): Returns a view of the portion of this Map whose keys range from fromKey, inclusive, to toKey, exclusive.
2. headMap(K toKey): Returns a view of the portion of this Map whose keys are strictly less than toKey.
3. tailMap(K fromKey): Returns a view of the portion of this Map whose keys are greater than or equal to fromKey.
4. firstKey(): Returns the first (lowest) key currently in this Map.
5. lastKey(): Returns the last (highest) key currently in this Map.
6. comparator(): Returns the Comparator used to order the keys in this Map, or null if this Map uses the natural ordering of its keys.
7. values​(): Returns a Collection view of the values contained in this map.
8. keySet​(): Returns a Set view of the keys contained in this map.
9. entrySet​(): Returns a Set view of the mappings contained in this map.

Code for SortedMap:

public interface SortedMap extends Map
{
    Comparator comparator();
    SortedMap subMap(K fromKey, K toKey);
    SortedMap headMap(K toKey);
    SortedMap tailMap(K fromKey);
    K firstKey();
    K lastKey();
}

Output:

Key : 1  value : geeksforgeeks
Key : 2  value : practice
Key : 3  value : quiz
Key : 4  value : contribute
Key : 5  value : code

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