IntelliJ IDEA not supporting Lambda?

Question

I'm working with this tutorial which uses lambda expressions.

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But IntelliJ says always: cannot resolve method(<lambda expression>) .

What do I have to check?

this.accountRepository.findByUsername(userId).orElseThrow(() -> new UserNotFoundException(userId));

Answer 1

You need to change the "Project language level" to "8 - Lambdas, type annotations etc.". You can find this option in "Project Settings" -> "Project"

Answer 2

It looks like your IntelliJ or your project is not setup to use Java 8.

1. Open Project Structure
2. Look into Project Settings | Project , the value of Project SDK should be 1.8
3. Look into Platform Settings | SDK , there should be 1.8 listed

It should look something like this:

Answer 3

In addition to the answers above look into you pom.xml file. Source and target should be 1.8 or higher. eg

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>