Add 80 comprehensive Java data types examples to data-types.md

[Copilot]

This PR adds a comprehensive guide to Java data types with 80 progressively advanced examples covering all major aspects of type representation, manipulation, and conversion in modern Java.

What's New

Created data-types.md with detailed examples demonstrating:

Core Data Types

• Primitive types: int, double, boolean, char, byte, short, long, float
• Reference types: String, List, Map, Set, and arrays
• Wrapper classes: Integer, Double, Boolean, Character

Type Operations

• Autoboxing/Unboxing: Automatic conversion between primitives and wrappers
• Type Conversion: Widening/narrowing conversions, explicit casting
• String Conversions: Parsing strings to primitives and vice versa

Modern Java Features

• Type Inference: Using var with primitives, collections, and generics
• Optional: Null-safe operations with Optional.of(), Optional.empty(), orElse()
• Pattern Matching: Type checking with instanceof patterns
• Records & Sealed Types: Modern immutable data carriers

Advanced Concepts

• Collections: Type-safe operations with List, Map, Set, ArrayList, HashMap
• Generics: Type bounds, wildcards, type erasure
• Comparison: Primitive vs reference equality, Comparable interface
• Precision Types: BigInteger and BigDecimal for arbitrary precision
• Concurrent Types: Atomic types for thread-safe operations

Implementation Details

All examples follow Java 25 syntax:

• ✅ Compact source file format with instance main methods
• ✅ Implicit imports (IO, List, Map, Set, ArrayList, HashMap)
• ✅ Type inference with var where appropriate
• ✅ Modern features like records, sealed interfaces, and type patterns

Examples are structured progressively from basic concepts (simple int/double types) to advanced patterns (type-safe heterogeneous containers, generic type bounds, atomic operations).

Each example includes:

• Concise, runnable code using void main()
• Clear description (max 80 chars/line) explaining the concept
• Practical demonstration of the type or operation

Formatting

Follows repository style guidelines:

• Descriptions limited to 80 characters per line with two-space endings
• No numbered section titles (plain descriptive names)
• Consistent with existing documentation (strings.md, conditionals.md)
• Functions referenced without parentheses

Fixes #<issue_number>

Original prompt

On data-types.md, Create 80 concise and progressively advanced Java examples that showcase the usage of Java data types. Each example should highlight a distinct type or concept related to data representation, manipulation, or conversion.

✅ Requirements

• Use modern Java syntax, including features up to Java 25:
  • Compact source files
  • Instance main methods
  • Type inference with var
  • Implicit imports (List, Map, IO, etc.)
• Cover a variety of data types and related topics:
  • Primitive types (int, double, boolean, char, byte, short, long, float)
  • Reference types (String, List, Map, Set, arrays)
  • Type inference with var
  • Wrapper classes (Integer, Double, etc.)
  • Autoboxing and unboxing
  • Type conversion and casting
  • Default values and initialization
  • Nullability and Optional
  • Using data types in collections
  • Comparison and equality

📄 Format

void main() {

    int age = 30;              
    double pi = 3.1415;           
    String name = "Java";         
    boolean isFun = true;        

    IO.println(name + " is fun: " + isFun + ", age: " + age + ", pi: " + pi);
}

Description:
Demonstrates usage of primitive and reference types with type inference.

🧠 Style Guidelines

• Use compact source file format (no class or static method unless necessary)
• Prefer IO.println for output
• Use var for type inference
• Keep examples readable and runnable
• Include a description (max 80 characters per line, two-space line endings)
• Refer to functions without parentheses (e.g. the main function)

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