Anjali

1. Functional Programming Enhancements

Java 8:
Java 8 introduced Lambda Expressions, which allow writing shorter, more readable code by eliminating the need for anonymous inner classes. For example:

  ```java
   // Without Lambda (Java 7)
  Runnable r = new Runnable() {
      @Override
      public void run() {
          System.out.println("Hello, World!");
      }
  }; 
  ```

// With Lambda (Java 8)

  ```java
   Runnable r = () -> System.out.println("Hello, World!"); 
  ```

Additionally, Streams API was introduced, which allows processing collections efficiently using a declarative approach. Streams enable operations like filtering, mapping, and reducing in a highly optimized way:

```java
 List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
List<String> filteredNames = names.stream()
                                  .filter(name -> name.startsWith("A"))
                                  .collect(Collectors.toList()); 
```

Java 21:
Java 21 builds on functional programming principles by introducing Pattern Matching for Switch, which eliminates redundant if-else statements and makes conditional logic clearer. Example:

  ```java
   Object obj = "Hello";
  
  switch (obj) {
      case String s -> System.out.println("String: " + s);
      case Integer i -> System.out.println("Integer: " + i);
      default -> System.out.println("Unknown type");
  } 
  ```

2. Performance Improvements

Java 8:

Java 8 primarily relied on Parallel GC and CMS GC, but both suffered from higher pause times under heavy workloads. The G1 Garbage Collector was introduced as the default, improving performance by breaking memory cleanup into smaller, incremental tasks rather than large disruptive sweeps.

Java 21:

Java 21 introduces ZGC (Z Garbage Collector) and Shenandoah GC, which dramatically reduce garbage collection pauses and enhance response time. Unlike G1 GC, ZGC is designed for low-latency applications, ensuring minimal disruptions even under high loads.

3. API & Library Improvements

Java 8:
Java 8 introduced the Date and Time API (java.time), replacing outdated java.util.Date.

Java 21:
Java 21 enhances String Templates, Foreign Function & Memory API, and introduces Structured Concurrency for better multi-threading support.

4. Long-Term Support (LTS)

Java 8:
Java 8 was an LTS release but is now outdated.

Java 21:
Java 21 is the latest LTS version, ensuring long-term security updates and stability.

5.Benefits of Upgrading to Java 21

a. String Templates (JEP 430)
	  Introduces templated strings, making string formatting more intuitive.
	  Reduces the need for manual concatenation.

b. Sequenced Collections (JEP 431)
	Introduces new collection interfaces that maintain a defined order of elements.
	Enhances List, Set, and Map to support predictable iteration order.

c. Improved Performance – Optimized garbage collection reduces latency.

d. Enhanced Security – Stronger encryption and security protocols.

e. Modern Syntax – Features like Records, Pattern Matching, and Virtual Threads make development more efficient.

f. Structured Concurrency (JEP 453)
	Simplifies multi-threaded programming by managing tasks in a structured way.
	Improves error handling and debugging in concurrent applications.