Update exercises/concept/international-calling-connoisseur/.docs/intr…

…oduction.md

Co-authored-by: Kah Goh <villastar@yahoo.com.au>

exercises/concept/international-calling-connoisseur/.docs/introduction.md

@@ -59,7 +59,7 @@ fruitPrices.size();  // Returns 2
 You can use the [keys] or [values] methods to obtain the keys or the values in a Map as a Set or collection respectively.
 
 ```java
-fruitPrices.keys();    // Returns "apple" and "pear" in a set
+fruitPrices.keySet();    // Returns "apple" and "pear" in a set
 fruitPrices.values();  // Returns 100 and 80, in a Collection
 ```