List.of gives error: cannot find symbol error

Question

I am using springboot with gradle and I am trying to execute below code in the controller.

List<String> planets
    = List.of("Mercury", "Venus", "Earth", "Mars",
    "Jupiter", "Saturn", "Uranus", "Neptune");

On compiling I get the following error

error: cannot find symbol = List.of("Mercury", "Venus", "Earth", "Mars", ^ symbol: method of(String,String,String,String,String,String,String,String)
location: interface List

my gradle file has

sourceCompatibility = '1.8'

I do understand that its a java 9 feature but unsure why would it fail on compile

It fails because you set the sourceCompatibility to 1.8... – Mark Rotteveel Aug 22 '20 at 18:17 — Mark Rotteveel, Aug 22 '20 at 18:17

score 12 · Accepted Answer · answered Aug 22 '20 at 08:53

12

List.of isn't a Java 9 feature, it's a method that was added in JDK 9. If you're using JDK 8, it just doesn't contain this method, and thus can't compile against it.

In short - use a newer JDK (and set the compatibility levels to 9 while you're at it, so you don't create a mix of valid Java 8 program that can only work with a newer JDK).

answered Aug 22 '20 at 08:53

Mureinik

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I see i am using java 13 in my machine.should List.of work without problem? where else should i be changing the version if i am using intellij on windows machine – hafiz ali Aug 22 '20 at 10:18
@Hafizallylalani Make sure IntelliJ is really using Java 13 as an SDK; set the language level in the project and set the `sourceCompatibility` and `targetCompatibility` in gradle. – Mureinik Aug 22 '20 at 10:22

score 5 · Answer 2 · answered Aug 12 '22 at 00:21

5

A quick fix is to replace List.of with Arrays.asList which is in JDK 8.

Note these methods are not quite identical, List.of returns an immutable list whereas Arrays.asList returns a mutable list. There are a few other differences listed here:

What is the difference between List.of and Arrays.asList?

answered Aug 12 '22 at 00:21

Daly

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As a possibility, Guava libraries includes an `ImmutableList` class (with `ImmutableList.of` method) if it were needed for an ancient JDK 8-based project. – BeardOverflow Jul 18 '23 at 12:50

List.of gives error: cannot find symbol error

2 Answers2