feat(streams): add demo of Primitive Streams (IntStream, DoubleStream) with ranges and random numbers

What
- Implemented `PrimitiveStreams` class showcasing usage of specialized primitive streams.
- Demonstrated:
  - `IntStream.range(1, 5)` → half-open range [1, 5).
  - `IntStream.rangeClosed(1, 5)` → inclusive range [1, 5].
  - `IntStream.of(1, 2, 3)` → creating primitive stream directly.
  - `DoubleStream` from `Random.doubles(5)` → generates 5 random doubles.
  - `IntStream` from `Random.ints(5)` → generates 5 random ints.
- Converted primitive streams to boxed object streams via `.boxed().collect(Collectors.toList())` for printing.

Why
- Primitive streams (`IntStream`, `DoubleStream`) avoid autoboxing overhead of `Stream<Integer>` or `Stream<Double>`.
- Provide specialized APIs (`sum()`, `average()`, `min()`, `max()`, `summaryStatistics()`).
- Useful in numerical-heavy domains like analytics, simulations, financial systems.
- Demonstrates difference between range vs rangeClosed and practical generation of random values.

Logic
1. **Creating Streams**
   - `Arrays.stream(numbers)` → from int[].
   - `IntStream.range(1, 5)` → produces `[1,2,3,4]`.
   - `IntStream.rangeClosed(1, 5)` → produces `[1,2,3,4,5]`.
   - `IntStream.of(1,2,3)` → direct literal stream.

2. **Random Primitive Streams**
   - `new Random().doubles(5)` → generates 5 random doubles.
   - `new Random().ints(5)` → generates 5 random integers.
   - Streams are infinite by default; specifying limit avoids unbounded generation.

3. **Boxing for Display**
   - `.boxed()` converts primitive values into wrapper objects (`Integer`, `Double`).
   - Collected into `List` for easy printing.

4. **Statistical APIs (commented for clarity)**
   - `.sum()`, `.min()`, `.max()`, `.average()`, `.summaryStatistics()`.
   - These methods directly support numerical operations without manual reduction.

Notes
- Use `.boxed()` only when interoperability with object-based APIs is required.
- Prefer primitive stream methods (`sum`, `average`) for performance.
- `range()` vs `rangeClosed()` → subtle but critical for loop-like semantics.

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

Author: Someshdiwan

JAVA8/StreamsInJAVA/PrimitiveStreams/src/PrimitiveStreams.java renamed to Java 8 Crash Course/Java 8 Streams/Primitive Streams/src/PrimitiveStreams.java

@@ -15,15 +15,15 @@ public static void main(String[] args) {
         IntStream.of(1, 2, 3);
 
         DoubleStream doubles = new Random().doubles(5);
-//        System.out.println(doubles.sum());
-//        System.out.println(doubles.min());
-//        System.out.println(doubles.max());
-//        System.out.println(doubles.average());
-//        doubles.summaryStatistics()
-//        doubles.mapToInt(x -> (int) (x + 1));
+        // System.out.println(doubles.sum());
+        // System.out.println(doubles.min());
+        // System.out.println(doubles.max());
+        // System.out.println(doubles.average());
+        // doubles.summaryStatistics()
+        // doubles.mapToInt(x -> (int) (x + 1));
         System.out.println(doubles.boxed().toList());
 
         IntStream intStream = new Random().ints(5);
         System.out.println(intStream.boxed().toList());
     }
-}
+}