Update 15/Nov/2023

Since version 5.x, mockito switched its default mock runner to mockito-inline.

Mockito 5 switches the default mockmaker to mockito-inline, and now requires Java 11 (see Mockito GitHub homepage)

Use mockito 5.x, if you cannot, follow previous answer below:

As the error message suggests, you cannot mock final classes with the default Mockito.

But the community came up with mockito-inline, an extension bringing experimental features such as mocking final classes and methods or static methods.

Just add this in your pom.xml and use Mockito normally.

<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-inline</artifactId>
    <scope>test</scope>
</dependency>

and for Gradle:

testImplementation 'org.mockito:mockito-inline:4.11.0'

You can use Mockito.reset(mock), just be aware that after you call it, your mock will forget all stubbing as well as all interactions, so you would need to set it up again. Mockito's documentation on the method has these usage instructions:

List mock = mock(List.class);
when(mock.size()).thenReturn(10);
mock.add(1);

reset(mock);
//at this point the mock forgot any interactions & stubbing

They do also discourage use of this method, like the comments on your question do. Usually it means you could refactor your test to be more focused:

Instead of reset() please consider writing simple, small and focused test methods over lengthy, over-specified tests. First potential code smell is reset() in the middle of the test method. This probably means you're testing too much. Follow the whisper of your test methods: "Please keep us small & focused on single behavior". There are several threads about it on mockito mailing list.