Java: How to dynamically add classes to the interface class in java

Question

I am pretty new to java, still a lot learn. I have created an interface class called FailedTest. After all of the tests run, I would like to add the failed tests classes to the FailedTest interface class. Once I have all of the failed tests, I would like to create a gradle task to run all of the failed tests again. I am using Junit, Intellij and Gradle.

FailedTest interface class in categories package:------

package myPackage.categories;

public interface FailedTests {
}

TestExecutionListener in listeners:----------

@Category(FailedTests.class)

public void afterTestExecution(TestContext testContext) {

  if (testContext.getTestException() != null) {

  // i would like to add failed tests to the FailedTest interface class here

   FailedTests = testContext.getTestClass();

  }
}

In build.gradle I would like create following task:----------

task testFailedTests(type: Test) {ext.getTestMethodsFromStorage = { ->

  //return a string array of the test classes/methods from the file:FailedTest 
  }

  useJUnit {

    include getTestMethodsFromStorage()

  }
}

I would appreciate any help or feedback. Thank you!