Home > Java > javaTutorial > body text

Why does casting `toArray()` result to `String[]` cause a `ClassCastException`?

Barbara Streisand
Release: 2024-11-02 04:03:03
Original
328 people have browsed it

Why does casting `toArray()` result to `String[]` cause a `ClassCastException`?

Unable to Convert toArray() Result to String[]

The following code consistently triggers a ClassCastException at line 3:

<code class="java">final String[] v1 = i18nCategory.translation.get(id);
final ArrayList<String> v2 = new ArrayList<>(Arrays.asList(v1));
String[] v3 = (String[])v2.toArray();</code>
Copy after login

This error persists regardless of whether v2 contains any elements or if its content exclusively comprises strings. What explains this behavior?

Resolution

toArray() returns an Object[], which cannot be directly cast to a String[] even if the elements in Object[] are strings. This is because generics are implemented at compile time only and are not present during runtime. As a result, toArray() cannot determine the intended array type.

To rectify this issue, use the following modified code:

<code class="java">String[] v3 = v2.toArray(new String[v2.size()]);</code>
Copy after login

This version creates an array of the correct type (String[]) with the appropriate length, eliminating the ClassCastException.

The above is the detailed content of Why does casting `toArray()` result to `String[]` cause a `ClassCastException`?. For more information, please follow other related articles on the PHP Chinese website!

source:php.cn
Statement of this Website
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
Latest Articles by Author
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template
About us Disclaimer Sitemap
php.cn:Public welfare online PHP training,Help PHP learners grow quickly!