Is lesson me hum seekhenge:

• Set kya hota hai
• Set ki properties
• Set implementations (HashSet, LinkedHashSet, TreeSet)
• Important methods
• Real examples

Set ek interface hai jo:

unique elements store karta hai

Features:

✔ duplicate elements allowed nahi
✔ unordered collection (mostly)
✔ null ek hi allow hota hai (HashSet me)

java.util.Set

Java me main Set implementations:

HashSet
LinkedHashSet
TreeSet

✔ unordered
✔ fast (hashing use karta hai)
✔ duplicate remove automatically

Example:

import java.util.*;

class Test {

    public static void main(String[] args){

        HashSet<Integer> set = new HashSet<>();

        set.add(10);
        set.add(20);
        set.add(10); // duplicate ignore

        System.out.println(set);
    }
}

✔ insertion order maintain karta hai
✔ thoda slow HashSet se

Example:

LinkedHashSet<String> set = new LinkedHashSet<>();

set.add("A");
set.add("B");
set.add("C");

System.out.println(set);

✔ sorted order me elements store karta hai
✔ internally tree structure use karta hai

Example:

TreeSet<Integer> set = new TreeSet<>();

set.add(30);
set.add(10);
set.add(20);

System.out.println(set); // sorted output

for(int n : set){
    System.out.println(n);
}

unique values store karna

Example:

usernames
emails
IDs

✔ Set duplicates automatically remove karta hai
✔ HashSet fastest hota hai
✔ TreeSet sorted data deta hai

1. Set kya hota hai?
2. HashSet aur TreeSet me difference?
3. Set me duplicate kyun allowed nahi?
4. TreeSet me null kyun allowed nahi?

Is lesson me humne seekha:

✔ Set interface
✔ HashSet, LinkedHashSet, TreeSet
✔ Important methods
✔ Differences aur use cases

Set Java me unique data store karne ke liye best collection hai.