When do we use interface extends interface

Question

I wish to know when we can use an interface extending another interface. I wish to know a practical example and when we use it.

Answer 1

You extend an interface when a subinterface provides everything the superinterface provides, and does something else of importance. For example, SortedMap<K,V> implements Map<K,V>, because sorted map is a map that supports all operations of a map, plus some operations applicable only to sorted maps.

This is similar to inheriting among classes, but it allows for multiple implementations. For example, one could implement a SortedMap as a sorted list of keys plus a parallel array of values, rather than a tree. This would let users swap in a faster or otherwise superior implementation without changing the rest of the code. In other words, inheritance among interfaces lets you preserve the benefits of programming to interfaces.