Understanding the Behavior of Raw Types with Generic Methods
When working with Java's generics, it is crucial to understand the implications of using raw types and their impact on generic methods. Let's delve into a specific code example and explore how raw types affect method resolution.
Consider the following code snippet, where an ArrayList of Strings is created and converted to an array:
ArrayList<string> a = new ArrayList<string>(); String[] s = a.toArray(new String[0]);</string></string>
As expected, this code compiles successfully in Java 1.6 and 1.7. However, if the ArrayList reference is declared as a raw type, an error occurs during compilation:
ArrayList a = new ArrayList(); String[] s = a.toArray(new String[0]); // Error: Argument required String[] found Object[]
In this scenario, the compiler interprets the generic method toArray(myArray) as returning an Object[] despite receiving a String[] as its argument. This behavior is quite unexpected, given that the method signature clearly specifies a type parameter
To understand this, let's consider the Java Language Specification (JLS) section 4.8. It states that "the type of an instance method M of a raw type C that is not inherited from its superclasses or superinterfaces is the raw type that corresponds to the erasure of its type in the generic declaration corresponding to C."
In essence, when using a raw type, the compiler essentially throws away all type information, leaving only the raw representation of the class. This means that, in our example, the toArray method effectively becomes a non-generic method with an Object[] return type, even though it was originally defined as a generic method.
This loss of genericity in raw types has important implications:
- Using raw types can make your code more susceptible to runtime type errors.
- Compiler warnings may not always be triggered when using raw types, leading to potential bugs.
It is generally recommended to avoid using raw types and instead rely on generics for type safety and flexibility. However, understanding the behavior of raw types can help you troubleshoot issues and make informed decisions in specific scenarios.
The above is the detailed content of Why Does Using Raw Types With Generic Methods Result in Unexpected Behavior?. For more information, please follow other related articles on the PHP Chinese website!

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

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

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

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

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.

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

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

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


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

SublimeText3 English version
Recommended: Win version, supports code prompts!

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)
