Annotate interfaces with @FunctionaInterface

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/cache/CacheStatisticsProvider.java

@@ -27,6 +27,7 @@
  * @author Phillip Webb
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface CacheStatisticsProvider<C extends Cache> {
 
 	/**

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/PublicMetrics.java

@@ -26,6 +26,7 @@
  * @author Dave Syer
  * @see SystemPublicMetrics
  */
+@FunctionalInterface
 public interface PublicMetrics {
 
 	/**

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/mvc/EndpointHandlerMappingCustomizer.java

@@ -22,6 +22,7 @@
  * @author Dave Syer
  * @since 1.2.0
  */
+@FunctionalInterface
 public interface EndpointHandlerMappingCustomizer {
 
 	/**

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/mvc/ManagementServletContext.java

@@ -22,6 +22,7 @@
  * @author Phillip Webb
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface ManagementServletContext {
 
 	/**

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/HealthAggregator.java

@@ -34,6 +34,7 @@
  * @author Christian Dupuis
  * @since 1.1.0
  */
+@FunctionalInterface
 public interface HealthAggregator {
 
 	/**

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/HealthIndicator.java

@@ -22,6 +22,7 @@
  * @author Dave Syer
  * @see ApplicationHealthIndicator
  */
+@FunctionalInterface
 public interface HealthIndicator {
 
 	/**

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/info/InfoContributor.java

@@ -22,6 +22,7 @@
  * @author Stephane Nicoll
  * @since 1.4.0
  */
+@FunctionalInterface
 public interface InfoContributor {
 
 	/**

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/GaugeService.java

@@ -27,6 +27,7 @@
  *
  * @author Dave Syer
  */
+@FunctionalInterface
 public interface GaugeService {
 
 	/**

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/export/Exporter.java

@@ -27,6 +27,7 @@
  * @author Dave Syer
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface Exporter {
 
 	/**

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/opentsdb/OpenTsdbNamingStrategy.java

@@ -22,6 +22,7 @@
  * @author Dave Syer
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface OpenTsdbNamingStrategy {
 
 	/**

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/reader/PrefixMetricReader.java

@@ -23,6 +23,7 @@
  *
  * @author Dave Syer
  */
+@FunctionalInterface
 public interface PrefixMetricReader {
 
 	/**

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/writer/GaugeWriter.java

@@ -24,6 +24,7 @@
  * @author Dave Syer
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface GaugeWriter {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/cache/CacheManagerCustomizer.java

@@ -26,6 +26,7 @@
  * @author Stephane Nicoll
  * @since 1.3.3
  */
+@FunctionalInterface
 public interface CacheManagerCustomizer<T extends CacheManager> {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/cache/JCacheManagerCustomizer.java

@@ -25,6 +25,7 @@
  * @author Stephane Nicoll
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface JCacheManagerCustomizer {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/flyway/FlywayMigrationStrategy.java

@@ -25,6 +25,7 @@
  * @author Andreas Ahlenstorf
  * @author Phillip Webb
  */
+@FunctionalInterface
 public interface FlywayMigrationStrategy {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jackson/Jackson2ObjectMapperBuilderCustomizer.java

@@ -28,6 +28,7 @@
  * @author Grzegorz Poznachowski
  * @since 1.4.0
  */
+@FunctionalInterface
 public interface Jackson2ObjectMapperBuilderCustomizer {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/metadata/DataSourcePoolMetadataProvider.java

@@ -24,6 +24,7 @@
  * @author Stephane Nicoll
  * @since 1.2.0
  */
+@FunctionalInterface
 public interface DataSourcePoolMetadataProvider {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jersey/ResourceConfigCustomizer.java

@@ -25,6 +25,7 @@
  * @author Eddú Meléndez
  * @since 1.4.0
  */
+@FunctionalInterface
 public interface ResourceConfigCustomizer {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jms/artemis/ArtemisConfigurationCustomizer.java

@@ -29,6 +29,7 @@
  * @since 1.3.0
  * @see ArtemisAutoConfiguration
  */
+@FunctionalInterface
 public interface ArtemisConfigurationCustomizer {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/AuthoritiesExtractor.java

@@ -28,6 +28,7 @@
  * @author Dave Syer
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface AuthoritiesExtractor {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/JwtAccessTokenConverterConfigurer.java

@@ -25,6 +25,7 @@
  * @author Dave Syer
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface JwtAccessTokenConverterConfigurer {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/PrincipalExtractor.java

@@ -25,6 +25,7 @@
  * @author Phillip Webb
  * @since 1.4.0
  */
+@FunctionalInterface
 public interface PrincipalExtractor {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/UserInfoRestTemplateCustomizer.java

@@ -29,6 +29,7 @@
  * @author Dave Syer
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface UserInfoRestTemplateCustomizer {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/template/TemplateAvailabilityProvider.java

@@ -26,6 +26,7 @@
  * @author Andy Wilkinson
  * @since 1.1.0
  */
+@FunctionalInterface
 public interface TemplateAvailabilityProvider {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ErrorController.java

@@ -24,6 +24,7 @@
  *
  * @author Phillip Webb
  */
+@FunctionalInterface
 public interface ErrorController {
 
 	/**

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ErrorViewResolver.java

@@ -29,6 +29,7 @@
  * @author Phillip Webb
  * @since 1.4.0
  */
+@FunctionalInterface
 public interface ErrorViewResolver {
 
 	/**

spring-boot-cli/src/main/java/org/springframework/boot/cli/command/CommandFactory.java

@@ -25,6 +25,7 @@
  *
  * @author Dave Syer
  */
+@FunctionalInterface
 public interface CommandFactory {
 
 	/**

spring-boot-cli/src/main/java/org/springframework/boot/cli/command/install/DependencyResolver.java

@@ -26,6 +26,7 @@
  * @author Andy Wilkinson
  * @since 1.2.0
  */
+@FunctionalInterface
 interface DependencyResolver {
 
 	/**

spring-boot-cli/src/main/java/org/springframework/boot/cli/compiler/SpringBootAstTransformation.java

@@ -24,6 +24,7 @@
  *
  * @author Dave Syer
  */
+@FunctionalInterface
 public interface SpringBootAstTransformation extends ASTTransformation {
 
 }

spring-boot-cli/src/main/java/org/springframework/boot/cli/compiler/grape/ProgressReporter.java

@@ -21,6 +21,7 @@
  *
  * @author Andy Wilkinson
  */
+@FunctionalInterface
 interface ProgressReporter {
 
 	/**

spring-boot-cli/src/main/java/org/springframework/boot/cli/compiler/grape/RepositorySystemSessionAutoConfiguration.java

@@ -25,6 +25,7 @@
  *
  * @author Andy Wilkinson
  */
+@FunctionalInterface
 public interface RepositorySystemSessionAutoConfiguration {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/classpath/ClassPathRestartStrategy.java

@@ -27,6 +27,7 @@
  * @since 1.3.0
  * @see PatternClassPathRestartStrategy
  */
+@FunctionalInterface
 public interface ClassPathRestartStrategy {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/filewatch/FileChangeListener.java

@@ -25,6 +25,7 @@
  * @author Phillip Webb
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface FileChangeListener {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/filewatch/FileSystemWatcherFactory.java

@@ -22,6 +22,7 @@
  * @author Phillip Webb
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface FileSystemWatcherFactory {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/remote/server/AccessManager.java

@@ -24,6 +24,7 @@
  * @author Phillip Webb
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface AccessManager {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/remote/server/Handler.java

@@ -27,6 +27,7 @@
  * @author Phillip Webb
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface Handler {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/remote/server/HandlerMapper.java

@@ -25,6 +25,7 @@
  * @author Phillip Webb
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface HandlerMapper {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/FailureHandler.java

@@ -22,6 +22,7 @@
  * @author Phillip Webb
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface FailureHandler {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/RestartInitializer.java

@@ -25,6 +25,7 @@
  * @since 1.3.0
  * @see DefaultRestartInitializer
  */
+@FunctionalInterface
 public interface RestartInitializer {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/RestartListener.java

@@ -22,6 +22,7 @@
  * @author Andy Wilkinson
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface RestartListener {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/classloader/ClassLoaderFileRepository.java

@@ -25,6 +25,7 @@
  * @since 1.3.0
  * @see ClassLoaderFile
  */
+@FunctionalInterface
 public interface ClassLoaderFileRepository {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/server/SourceFolderUrlFilter.java

@@ -26,6 +26,7 @@
  * @since 1.3.0
  * @see DefaultSourceFolderUrlFilter
  */
+@FunctionalInterface
 public interface SourceFolderUrlFilter {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/tunnel/client/TunnelConnection.java

@@ -25,6 +25,7 @@
  * @author Phillip Webb
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface TunnelConnection {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/tunnel/server/PortProvider.java

@@ -23,6 +23,7 @@
  * @author Phillip Webb
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface PortProvider {
 
 	/**

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/tunnel/server/TargetServerConnection.java

@@ -25,6 +25,7 @@
  * @author Phillip Webb
  * @since 1.3.0
  */
+@FunctionalInterface
 public interface TargetServerConnection {
 
 	/**

spring-boot-parent/pom.xml

@@ -19,7 +19,7 @@
 	<properties>
 		<main.basedir>..</main.basedir>
 		<disable.checks>false</disable.checks>
-		<java.version>1.6</java.version>
+		<java.version>1.8</java.version>
 		<aether.version>1.0.2.v20150114</aether.version>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

spring-boot-test-autoconfigure/src/main/java/org/springframework/boot/test/autoconfigure/restdocs/RestDocsMockMvcConfigurationCustomizer.java

@@ -29,6 +29,7 @@
  * @author Andy Wilkinson
  * @since 1.4.0
  */
+@FunctionalInterface
 public interface RestDocsMockMvcConfigurationCustomizer {
 
 	/**

spring-boot-test-autoconfigure/src/main/java/org/springframework/boot/test/autoconfigure/web/servlet/MockMvcBuilderCustomizer.java

@@ -28,6 +28,7 @@
  * @since 1.4.0
  * @see MockMvcAutoConfiguration
  */
+@FunctionalInterface
 public interface MockMvcBuilderCustomizer {
 
 	/**

spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/fieldvalues/FieldValuesParser.java

@@ -30,6 +30,7 @@
  * @since 1.1.2
  * @see JavaCompilerFieldValuesParser
  */
+@FunctionalInterface
 public interface FieldValuesParser {
 
 	/**