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CollectionClass.java
CollectionClass.java
 
 
readme.md
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readme.md

☕ Java Lesson – Collections Class (Utility Class)

Is lesson me hum seekhenge:

  • Collections class kya hoti hai
  • Collection vs Collections difference
  • Important methods of Collections class
  • Sorting, reversing, searching operations
  • Real examples

1️⃣ Collections Class Kya Hoti Hai?

Collections ek utility class hai jo provide karti hai:

static methods for collection operations

Ye class:

java.util package me hoti hai

2️⃣ Collection vs Collections

Feature Collection Collections
Type Interface Class
Use data store karna operations perform karna

3️⃣ Common Methods of Collections Class

Method Use
sort() sorting
reverse() reverse order
max() maximum value
min() minimum value
shuffle() random order
binarySearch() searching
frequency() count occurrences

4️⃣ Sorting Example

import java.util.*;

class Test {

    public static void main(String[] args){

        ArrayList<Integer> list = new ArrayList<>();

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

        Collections.sort(list);

        System.out.println(list);
    }
}

Output:

[10, 20, 30]

5️⃣ Reverse Example

Collections.reverse(list);

6️⃣ Max and Min

System.out.println(Collections.max(list));
System.out.println(Collections.min(list));

7️⃣ Shuffle Example

Collections.shuffle(list);

Random order me elements arrange honge.

8️⃣ Binary Search

Collections.sort(list);

int index = Collections.binarySearch(list, 20);

System.out.println(index);

Note:

list sorted hona chahiye

9️⃣ Frequency Count

int count = Collections.frequency(list, 10);

System.out.println(count);

🔟 Custom Object Sorting

Collections.sort(list, Comparator.reverseOrder());

1️⃣1️⃣ Immutable Collection

List<Integer> list = Collections.unmodifiableList(new ArrayList<>());

Isme modification allowed nahi.

1️⃣2️⃣ Real-Life Example

import java.util.*;

class Test {

    public static void main(String[] args){

        ArrayList<String> names = new ArrayList<>();

        names.add("Sujit");
        names.add("Rahul");
        names.add("Amit");

        Collections.sort(names);

        System.out.println(names);
    }
}

1️⃣3️⃣ Important Points

✔ Collections class ke sab methods static hote hain
✔ Ye sirf operations perform karti hai
✔ Data store nahi karti

🎯 Interview Questions

  1. Collection aur Collections me difference kya hai?
  2. Collections.sort() kaise kaam karta hai?
  3. Binary search me sorting kyun zaruri hai?
  4. shuffle() method ka use kya hai?

🧾 Lesson Summary

Is lesson me humne seekha:

✔ Collections class concept
✔ Important utility methods
✔ Sorting, searching, reversing
✔ Real-life examples

Collections class Java me collection operations ko easy aur efficient banati hai.