new: added map and max min methods from stream apis

java8/PROBLEMS.md

@@ -1,47 +1,142 @@
 # Java 8 Problems & Concepts
 
-## Completed Problems
+## 📂 Module Structure
 
-### ✅ Q001: Print All Numbers
-**Location:** `java8/Q001_print_numbers/`  
+```
+java8/
+├── pom.xml                          # Module build configuration
+├── README.md                        # Module overview and quick start
+├── PROBLEMS.md                      # This file - problem statements and status
+├── LEARNING_STRUCTURE.md            # Complete learning guide
+├── PROBLEM_TEMPLATE.md              # Template for adding new problems
+├── Troubleshoot.md                  # Common errors and solutions
+├── src/
+│   └── main/
+│       └── java/
+│           └── com/modernjava/guide/
+│               ├── Main.java                                    # Module entry point
+│               └── java8/
+│                   ├── Q001_print_numbers/
+│                   │   ├── PrintNumbersComparison.java          # ✅ Complete
+│                   │   ├── PrintNumbersStream.java              # ✅ Complete
+│                   │   └── PrintNumbersTraditional.java         # ✅ Complete
+│                   ├── Q002_print_evens/
+│                   │   ├── PrintEvensComparison.java            # ✅ Complete
+│                   │   ├── PrintEvensStream.java                # ✅ Complete
+│                   │   └── PrintEvensTraditional.java           # ✅ Complete
+│                   ├── Q003_square_nums/
+│                   │   ├── SumOfSquareOfNumberComparison.java   # ✅ Complete
+│                   │   ├── SumOfSquareOfNumberStream.java       # ✅ Complete
+│                   │   └── SumOfSquareOfNumberTraditional.java  # ✅ Complete
+│                   ├── Q004_max_min/
+│                   │   ├── MaxMinNumberComparison.java          # ✅ Complete
+│                   │   ├── MaxMinNumberStream.java              # ✅ Complete
+│                   │   ├── MaxMinNumberTraditional.java         # ✅ Complete
+│                   │   └── Pair.java                            # ✅ Helper class
+│                   └── util/
+│                       └── ComparisonUtils.java                 # ✅ Shared utilities
+└── target/                          # Compiled output (not tracked in git)
+```
+
+---
+
+## ✅ Completed Problems
+
+### Q001: Print All Numbers
+**Location:** `com.modernjava.guide.java8.Q001_print_numbers`  
 **Concepts:** Stream basics, forEach(), method references, lambda expressions  
-**Problem:** Print all numbers in a list  
+**Problem:** Print all numbers in an array  
 **Input:** `[1, 2, 1, 3, 2, 4, 5, 6, 2, 2, 7, 8, 4, 9, 10]`  
 **Traditional:** for-each loop  
-**Stream:** `numbers.stream().forEach(System.out::println)`
+**Stream:** `Arrays.stream(numbers).forEach(System.out::println)`  
+**Comparison:** ✅ `PrintNumbersComparison.java`
 
 ---
 
-## Partially Completed
-
-### ⚠️ Q002: Print Even numbers
-**Location:** `java8/Q002_print_evens/`  
-**Concepts:** filter(), forEach(), method references, lambda expressions  
-**Problem:** Print all even numbers present within a list  
-**Input:** `[1, 2, 3, 4, 5]` → **Output:** `2,4`  
-**Traditional:** ✅ `PrintEvensTraditional.java`  
-**Stream:** ✅ `PrintEvensStream.java`  
+### Q002: Print Even Numbers
+**Location:** `com.modernjava.guide.java8.Q002_print_evens`  
+**Concepts:** filter(), forEach(), predicates, lambda expressions  
+**Problem:** Print all even numbers present within an array  
+**Input:** `[1, 2, 3, 4, 5]` → **Output:** `2, 4`  
+**Traditional:** ✅ `PrintEvensTraditional.java` - for loop with modulo check  
+**Stream:** ✅ `PrintEvensStream.java` - `filter(n -> n % 2 == 0)`  
 **Comparison:** ✅ `PrintEvensComparison.java`
 
 ---
 
-## Core Concepts Covered
+### Q003: Sum of Square of Numbers
+**Location:** `com.modernjava.guide.java8.Q003_square_nums`  
+**Concepts:** map(), reduce(), sum(), transformations  
+**Problem:** Calculate sum of squares of all numbers in an array  
+**Input:** `[1, 2, 3, 4, 5]` → **Output:** `55` (1² + 2² + 3² + 4² + 5²)  
+**Traditional:** ✅ `SumOfSquareOfNumberTraditional.java` - for loop with accumulator  
+**Stream:** ✅ `SumOfSquareOfNumberStream.java` - `map(n -> n * n).sum()`  
+**Comparison:** ✅ `SumOfSquareOfNumberComparison.java` - includes performance benchmarks
+
+---
+
+### Q004: Find Max and Min Numbers
+**Location:** `com.modernjava.guide.java8.Q004_max_min`  
+**Concepts:** max(), min(), Comparator, Optional handling  
+**Problem:** Find both maximum and minimum values in an array  
+**Input:** `[45, 22, 89, 11, 67, 34, 90, 5, -121, 342, 0, 9999, -5000]`  
+**Output:** `Max = 9999, Min = -5000`  
+**Traditional:** ✅ `MaxMinNumberTraditional.java` - single pass with variables  
+**Stream:** ✅ `MaxMinNumberStream.java` - `max()` and `min()` terminal operations  
+**Comparison:** ✅ `MaxMinNumberComparison.java` - multiple test cases with varying sizes  
+**Helper:** ✅ `Pair.java` - simple class to hold max/min result
+
+---
+
+## 🛠️ Utility Classes
+
+### ComparisonUtils
+**Location:** `com.modernjava.guide.java8.util.ComparisonUtils`  
+**Purpose:** Shared helper methods for all comparison classes
+
+**Methods:**
+- `repeat(String str, int count)` - Repeats string N times (Java 8 compatible alternative to String.repeat())
+- `formatTime(long nanos)` - Formats nanoseconds to human-readable format (ns, μs, ms)
+- `printNumbers(int[] numbers)` - Prints array elements comma-separated
+- `getArrayOfSpecifiedSize(int size)` - Generates random int array with positive, negative, and zero values (range: -100 to +100)
+
+---
+
+## 🎯 Core Concepts Covered
 
 ### Stream Operations
-- **Terminal Operations:** `forEach()`, `count()`, `sum()`
+- **Terminal Operations:** `forEach()`, `count()`, `sum()`, `max()`, `min()`
 - **Intermediate Operations:** `filter()`, `map()`
-- **Method References:** `System.out::println`, `Integer::intValue`
+- **Method References:** `System.out::println`, `Integer::compare`
 - **Lambda Expressions:** `n -> n % 2 == 0`, `n -> n * n`
 
 ### Comparison Topics
 - Traditional vs Stream syntax
 - Performance analysis with JIT warmup
 - Code readability and maintainability
 - When to use each approach
+- Handling edge cases (empty arrays, single elements)
+
+### Java 8 Features Demonstrated
+- ✅ Lambda expressions
+- ✅ Method references
+- ✅ Stream API basics
+- ✅ Functional interfaces
+- ✅ Optional (in max/min operations)
+
+---
+
+## 📊 Performance Notes
+
+Based on benchmark results in comparison classes:
+- **Small arrays (< 100 elements):** Traditional approach is faster due to Stream overhead
+- **Large arrays (10,000+ elements):** Stream performance improves, gap narrows
+- **Very large arrays (1,000,000+ elements):** Traditional still edges out for simple operations
+- **Takeaway:** Use Streams for readability and composition, not raw speed in tight loops
 
 ---
 
-## Planned Problems
+## 🚧 Planned Problems
 
 ### Easy
 - Q003: Print even numbers only