Update README.md

Author: aatul

README.md

@@ -66,6 +66,85 @@ Collections are used to perform the following operations:
 ---
 
 ### 8. Explain about Set and their types in a collection?
+**Set**
+Set cares about uniqueness. It doesn’t allow duplicates. Here the “equals ( )” method is used to determine whether two objects are identical or not.
+
+**Hash Set:**
+*Unordered and unsorted.
+*Uses the hash code of the object to insert the values.
+*Use this when the requirement is “no duplicates and don’t care about the order”.
+
+Example:
+```java
+public class Fruit {
+ public static void main (String[] args){
+ HashSet<String> names = new HashSet <=String>();
+ names.add(“banana”);
+ names.add(“cherry”);
+ names.add(“apple”);
+ names.add(“kiwi”);
+ names.add(“banana”);
+ System.out.println(names);
+ }
+}
+```
+Output:
+
+[banana, cherry, kiwi, apple]
+
+Doesn’t follow any insertion order. Duplicates are not allowed.
+
+**Linked Hash set:**
+*An ordered version of the hash set is known as Linked Hash Set.
+*Maintains a doubly-Linked list of all the elements.
+*Use this when the iteration order is required.
+
+Example:
+```java
+public class Fruit {
+ public static void main (String[] args){
+ LinkedHashSet<String> names = new LinkedHashSet <String>();
+ names.add(“banana”);
+ names.add(“cherry”);
+ names.add(“apple”);
+ names.add(“kiwi”);
+ names.add(“banana”);
+ System.out.println(names);
+ }
+}
+```
+Output:
+
+[banana, cherry, apple, kiwi]
+
+Maintains the insertion order in which they have been added to the Set. Duplicates are not allowed.
+
+**Tree Set:**
+*It is one of the two sorted collections.
+*Uses “Read-Black” tree structure and guarantees that the elements will be in an ascending order.
+*We can construct a tree set with the constructor by using comparable (or) comparator.
+
+Example:
+```java
+public class Fruits{
+ public static void main (String[] args) {
+ Treeset<String> names= new TreeSet<String>();
+ names.add(“cherry”);
+ names.add(“banana”);
+ names.add(“apple”);
+ names.add(“kiwi”);
+ names.add(“cherry”);
+ System.out.println(names);
+ }
+}
+```
+Output:
+
+[apple, banana, cherry, kiwi]
+
+TreeSet sorts the elements in an ascending order. And duplicates are not allowed.
+
+
 ---
 
 ### 9. What is the final keyword in Java?