Java 8 and Java 17

Java 8 vs Java 17

Release Date and LTS Status
🔸 Java 8 was released in March 2014 and is a Long-Term Support version
🔸 Java 17 was released in September 2021 and is also an LTS version

Language Features

Java 8
🔸 Lambda Expressions allow passing behavior as parameters
🔸 Stream API enables functional-style operations on collections
🔸 Default Methods allow interfaces to have implementations
🔸 Optional Class helps avoid null pointer exceptions
🔸 New Date and Time API improves date handling

Java 17
🔸 Pattern Matching for instanceof reduces boilerplate code
🔸 Records reduce boilerplate for data classes
🔸 Sealed Classes restrict class inheritance
🔸 Text Blocks simplify multiline strings
🔸 Switch Expressions make switch more powerful
🔸 Foreign Function and Memory API provides low-level native access

Performance Improvements
🔸 Java 8 introduced performance improvements with Stream API
🔸 Java 17 improves JVM performance with better garbage collection and optimizations

Garbage Collection
🔸 Java 8 uses Parallel GC by default
🔸 Java 17 introduces ZGC and improved G1 for better memory management

Security Enhancements
🔸 Java 8 includes basic security improvements
🔸 Java 17 provides stronger security with modern cryptography and TLS

Modularity
🔸 Java 8 does not support modular system
🔸 Java 17 supports JPMS for modular applications

JDK Tools and Enhancements
🔸 Java 8 has basic tools
🔸 Java 17 includes advanced tools like Flight Recorder and JVM logging

Removed Features
🔸 Java 17 removes deprecated APIs like Applet

Backward Compatibility
🔸 Java 8 is widely used and stable
🔸 Java 17 supports backward compatibility but may require updates

Ecosystem Support
🔸 Java 8 is widely supported
🔸 Java 17 is optimized for modern frameworks

Conclusion
🔸 Java 8 is suitable for stable environments
🔸 Java 17 is better for modern applications with new features and performance

HashMap in Java

Working of HashMap

Internal Structure
🔸 HashMap uses buckets and hashing
🔸 It stores data in an array of linked lists or trees
🔸 Hash code determines bucket index
🔸 Collisions are handled using linked list or red-black tree

Insertion Operation
🔸 Hash code is calculated
🔸 Bucket index is determined
🔸 Value is inserted or updated
🔸 Resizing happens when load factor exceeds threshold

Retrieval Operation
🔸 Hash code is calculated
🔸 Bucket is located
🔸 Key is searched and value returned

Collision Handling
🔸 Multiple keys in same bucket are handled using linked list or tree

Uses of HashMap
🔸 Used for caching data
🔸 Used for configuration storage
🔸 Used as dictionary
🔸 Used for frequency counting
🔸 Used for grouping data
🔸 Used as associative array

Advantages of HashMap
🔸 Fast access with O(1) complexity
🔸 Flexible with null keys and values
🔸 Dynamic memory usage

Limitations of HashMap
🔸 Not thread-safe
🔸 Does not maintain order

Stream API in Java

Working of Stream API

Concepts
🔸 Streams process data without storing it
🔸 Collections store data
🔸 Intermediate operations transform stream
🔸 Terminal operations produce result

Pipeline
🔸 Stream pipeline includes source, intermediate and terminal operations

Workflow
🔸 Create stream from source
🔸 Apply intermediate operations
🔸 Execute terminal operation

Uses of Stream API
🔸 Filtering data
🔸 Transforming data
🔸 Sorting data
🔸 Aggregating data
🔸 Collecting data
🔸 Parallel processing

Advantages of Stream API
🔸 Declarative programming style
🔸 Lazy evaluation
🔸 Supports parallel processing
🔸 Improves readability

Limitations of Stream API
🔸 Can introduce overhead
🔸 Not suitable for all cases