search
HomeJavajavaTutorialHow Does Java\'s Enum Generic Type Parameter `E extends Enum` Work?

How Does Java's Enum Generic Type Parameter `E extends Enum` Work?

Java Enum Definition: Understanding Generics with Type Parameters

Java's Enum class employs a peculiar type parameter that may initially seem confusing:

class Enum<e extends enum>></e>

This parameter means that an enum type must derive from another enum type with the same type argument. In practice, the type argument is the enum type itself, as seen in this example:

public enum StatusCode extends Enum<statuscode></statuscode>

In this scenario, E is equivalent to StatusCode. Thus, E extends Enum, fulfilling the parameter's requirement.

This construct allows the Enum API to refer to itself, such as in Enum implements Comparable. The base class can perform comparisons while ensuring that only the appropriate enums are compared.

A similar concept is observed in C# with ProtocolBuffers' interfaces:

public interface IBuilder<tmessage tbuilder>
  where TMessage : IMessage<tmessage tbuilder> 
  where TBuilder : IBuilder<tmessage tbuilder>

public interface IMessage<tmessage tbuilder>
  where TMessage : IMessage<tmessage tbuilder> 
  where TBuilder : IBuilder<tmessage tbuilder></tmessage></tmessage></tmessage></tmessage></tmessage></tmessage>

This ensures that messages and builders can be paired appropriately.

It's worth noting that the type parameter does not prevent inconsistencies. For example, the following types would be valid:

public class First extends Enum<first> {}
public class Second extends Enum<first> {}</first></first>

In this case, Second would implement Comparable instead of Comparable, which can lead to unexpected behavior. However, the intention of the type parameter is to provide benefits in valid cases, not necessarily to enforce consistent usage.

The above is the detailed content of How Does Java\'s Enum Generic Type Parameter `E extends Enum` Work?. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Top 4 JavaScript Frameworks in 2025: React, Angular, Vue, SvelteTop 4 JavaScript Frameworks in 2025: React, Angular, Vue, SvelteMar 07, 2025 pm 06:09 PM

This article analyzes the top four JavaScript frameworks (React, Angular, Vue, Svelte) in 2025, comparing their performance, scalability, and future prospects. While all remain dominant due to strong communities and ecosystems, their relative popul

Spring Boot SnakeYAML 2.0 CVE-2022-1471 Issue FixedSpring Boot SnakeYAML 2.0 CVE-2022-1471 Issue FixedMar 07, 2025 pm 05:52 PM

This article addresses the CVE-2022-1471 vulnerability in SnakeYAML, a critical flaw allowing remote code execution. It details how upgrading Spring Boot applications to SnakeYAML 1.33 or later mitigates this risk, emphasizing that dependency updat

How do I implement multi-level caching in Java applications using libraries like Caffeine or Guava Cache?How do I implement multi-level caching in Java applications using libraries like Caffeine or Guava Cache?Mar 17, 2025 pm 05:44 PM

The article discusses implementing multi-level caching in Java using Caffeine and Guava Cache to enhance application performance. It covers setup, integration, and performance benefits, along with configuration and eviction policy management best pra

Node.js 20: Key Performance Boosts and New FeaturesNode.js 20: Key Performance Boosts and New FeaturesMar 07, 2025 pm 06:12 PM

Node.js 20 significantly enhances performance via V8 engine improvements, notably faster garbage collection and I/O. New features include better WebAssembly support and refined debugging tools, boosting developer productivity and application speed.

How does Java's classloading mechanism work, including different classloaders and their delegation models?How does Java's classloading mechanism work, including different classloaders and their delegation models?Mar 17, 2025 pm 05:35 PM

Java's classloading involves loading, linking, and initializing classes using a hierarchical system with Bootstrap, Extension, and Application classloaders. The parent delegation model ensures core classes are loaded first, affecting custom class loa

Iceberg: The Future of Data Lake TablesIceberg: The Future of Data Lake TablesMar 07, 2025 pm 06:31 PM

Iceberg, an open table format for large analytical datasets, improves data lake performance and scalability. It addresses limitations of Parquet/ORC through internal metadata management, enabling efficient schema evolution, time travel, concurrent w

How to Share Data Between Steps in CucumberHow to Share Data Between Steps in CucumberMar 07, 2025 pm 05:55 PM

This article explores methods for sharing data between Cucumber steps, comparing scenario context, global variables, argument passing, and data structures. It emphasizes best practices for maintainability, including concise context use, descriptive

How can I implement functional programming techniques in Java?How can I implement functional programming techniques in Java?Mar 11, 2025 pm 05:51 PM

This article explores integrating functional programming into Java using lambda expressions, Streams API, method references, and Optional. It highlights benefits like improved code readability and maintainability through conciseness and immutability

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

Hot Tools

MantisBT

MantisBT

Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

Atom editor mac version download

Atom editor mac version download

The most popular open source editor

Dreamweaver Mac version

Dreamweaver Mac version

Visual web development tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 English version

SublimeText3 English version

Recommended: Win version, supports code prompts!