Merge pull request #15666 from izeye

* pr/15666:
  Polish "Remove an unused interface in RestarterTests"
  Remove an unused interface in RestarterTests

spring-boot-project/spring-boot-devtools/src/test/java/org/springframework/boot/devtools/restart/RestarterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -176,13 +176,6 @@ public class RestarterTests {
 		assertThat(Restarter.getInstance().getInitialUrls()).isEqualTo(urls);
 	}
 
-	@FunctionalInterface
-	private interface WithMainAction {
-
-		void perform() throws Exception;
-
-	}
-
 	@Component
 	@EnableScheduling
 	public static class SampleApplication {