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Java 8 vs 11 vs 17 vs 21

A detailed comparison of Java 8, Java 11, Java 17, and Java 21, summarizing the key differences, improvements, and deprecations introduced across these versions:

Java 8 (Released March 2014)

Java 8 is a long-term support (LTS) release, bringing significant new features:

Major Features

  • Lambda Expressions: Enables functional-style programming.
  • Stream API: Helps process collections and data pipelines.
  • Optional Class: Helps avoid NullPointerException.
  • Default Methods in Interfaces: Allows adding new methods to interfaces without breaking existing code.
  • New Date and Time API (java.time): Replaces the old java.util.Date.
  • Nashorn JavaScript Engine: Allows embedding JavaScript in Java applications.

Performance & Security

  • PermGen space removed (replaced by Metaspace).
  • Improved Garbage Collection (G1 GC available).

Drawbacks

  • Older TLS 1.2 implementation.
  • Less modular structure.

Java 11 (Released Sept 2018)

Java 11 is also LTS and a significant milestone since it removed many outdated APIs and modularized the runtime.

Major Features

  • Local-Variable Syntax for Lambda Parameters (var in lambda).
  • HTTP Client API (Standardized): Supports HTTP/2.
  • String Enhancements: lines(), strip(), repeat(), isBlank() methods.
  • Files API Improvements: readString(), writeString(), isSameFile() methods.
  • Nest-Based Access Control: Easier access between nested classes.
  • ZGC (Z Garbage Collector): A scalable low-latency GC.

Removals & Deprecations

  • Removal of Java EE and CORBA modules.
  • Nashorn JavaScript Engine deprecated.
  • Applet API deprecated.

Performance & Security

  • TLS 1.3 support.
  • Better memory management (e.g., with ZGC).

Java 17 (Released Sept 2021)

Java 17 is an LTS release, refining many features introduced in Java 9-16 and stabilizing the platform.

Major Features

  • Sealed Classes: Restricts which classes can extend or implement a particular class.
  • Pattern Matching for instanceof: Simplifies type casting.
  • Records: Concise way to model immutable data.
  • Text Blocks: Multi-line string literals.
  • Foreign Function and Memory API (Preview): Facilitates interoperation with native libraries.
  • Enhanced Switch (Pattern Matching, Switch Expressions).

Removals & Deprecations

  • Deprecated Security Manager.
  • RMI Activation removed.
  • Applet API removed.

Garbage Improvements

  • ZGC and Shenandoah GC production-ready.

Performance & Security

  • Stronger encapsulation in the JDK modules.
  • Better startup, memory, and GC performance.

Java 21 (Released Sept 2023)

Java 21 is a non-LTS release (though with unofficial support from some vendors). It introduces many experimental and innovative features.

Major Features

  • Virtual Threads (Part of Project Loom): Lightweight threads for highly scalable applications.
  • Structured Concurrency (Incubator): Simplifies working with multiple concurrent tasks.
  • Record Patterns (Preview): Extends pattern matching.
  • Unnamed Patterns and Variables: Reduces verbosity when matching.
  • Sequenced Collections: New List, Set, and Map with defined iteration order.
  • String Templates: Simplifies string formatting.

Removals & Deprecations:

  • Security Manager fully removed.
  • Deprecated APIs cleaned up.

Performance & Security:

  • Further GC enhancements (ZGC, Shenandoah).
  • Virtual threads allow non-blocking I/O models, improving scalability.

Key Versions Differences

Feature / Change Java 8 Java 11 Java 17 Java 21
LTS Release Yes Yes Yes No
Lambda Expressions Yes Yes Yes Yes
HTTP Client No Yes (HTTP/2) Yes Yes
Modular System (JPMS) No Yes Yes Yes
Records No No Yes Yes
Sealed Classes No No Yes Yes
Text Blocks No No Yes Yes
Pattern Matching (instanceof) No No Yes Yes
Virtual Threads (Loom) No No No Yes
Garbage Collectors G1 GC ZGC ZGC, Shenandoah Improved ZGC, Shenandoah
String Enhancements Basic strip(), repeat() Text Blocks String Templates
TLS Version 1.2 1.3 1.3 1.3
Security Manager Available Deprecated Deprecated Removed
Nashorn JavaScript Engine Yes Deprecated Removed Removed

Summary

  • Java 8: Best suited for legacy systems; widely adopted but outdated.
  • Java 11: A stable upgrade for Java 8 users with modern features and TLS 1.3.
  • Java 17: The most recommended LTS version, offering modern features like records, sealed classes, and better performance.
  • Java 21: Introduces bleeding-edge technology such as virtual threads and structured concurrency, but being non-LTS, it’s suitable for developers eager to experiment or early adopters.

For production systems, upgrading to Java 17 is generally recommended unless your project needs experimental features from Java 21.