feat(HashMapPractice): demonstrate custom load factor, duplicate key handling, conditional remove

What
- Added `HashMapPractice` to explore advanced `HashMap` operations and behaviors:
  - Custom capacity and load factor initialization.
  - Duplicate key insertion (value replacement).
  - Conditional removal using `remove(key, value)`.
  - Checking membership with `List.contains()`.

Why
- Helps understand internal HashMap tuning (`initialCapacity`, `loadFactor`).
- Demonstrates how HashMap handles **duplicate keys** (latest value overwrites old one).
- Shows usage of `remove(Object key, Object value)` which only removes if both match.
- Illustrates interoperability with `List.contains()` for simple membership checks.

How
1. Created a `HashMap<Integer, String>` with **initial capacity = 17** and **load factor = 0.5**.
   - Load factor `0.5` means rehashing will occur when the table is half full (more frequent resizing).
2. Inserted entries:
   - `(31, "Shubham")`
   - `(11, "Akshit")`
   - `(2, "Neha")`, then `(2, "Mehul")` → key `2` updated, "Neha" replaced with "Mehul".
3. Used `remove(31, "Nitin")`:
   - Fails because value did not match (`map` still contains `31=Shubham`).
   - Returns `false`.
4. Demonstrated `List.contains(32)` on a fixed list `[2, 4, 32, 43, 4, 432]` → returns `true`.

Key Notes
- **Duplicate keys** overwrite old values, size does not increase.
- `remove(key, value)` = safe way to delete only if mapping matches exactly.
- Load factor tuning is rarely needed; default `0.75f` balances performance & memory.
- `HashMap` iteration order is **unpredictable**.

Real-world usage
- Custom load factor may be used for memory-sensitive or performance-critical scenarios.
- Conditional removal ensures correctness in concurrent or multi-thread contexts.
- Membership checks in lists/maps are common in data filtering pipelines.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan

Section25CollectionFramework/src/HashMapDemo/HashMapPractice.java renamed to Section 25 Collections Frameworks/Map Interface/HashMap/src/HashMapPractice.java

@@ -1,20 +1,22 @@
-package HashMapDemo;
-
 import java.util.*;
 public class HashMapPractice {
     public static void main(String[] args) {
         HashMap<Integer, String> map = new HashMap<>(17,0.5f);
+
         map.put(31, "Shubham");
         map.put(11, "Akshit");
         map.put(2, "Neha");
         map.put(2, "Mehul");
+
         System.out.println(map);
 
         boolean res = map.remove(31, "Nitin");
+
         System.out.println("REMOVED ? :" + res);
         System.out.println(map);
 
         List<Integer> list = Arrays.asList(2, 4, 32, 43, 4, 432);
+
         System.out.println(list.contains(32));
     }
-}
+}