Use lambdas when possible

Replace anonymous inner classes with lambda declarations (when possible
using method references).

See gh-9781

spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/StartMojo.java

@@ -228,14 +228,7 @@ public class StartMojo extends AbstractRunMojo {
 		final SpringApplicationAdminClient client = new SpringApplicationAdminClient(
 				connection, this.jmxName);
 		try {
-			execute(this.wait, this.maxAttempts, new Callable<Boolean>() {
-
-				@Override
-				public Boolean call() throws Exception {
-					return (client.isReady() ? true : null);
-				}
-
-			});
+			execute(this.wait, this.maxAttempts, () -> (client.isReady() ? true : null));
 		}
 		catch (ReflectionException ex) {
 			throw new MojoExecutionException("Unable to retrieve 'ready' attribute",