Use diamond operator where possible (#6764)

core/src/test/java/hudson/ChannelRule.java

@@ -33,13 +33,13 @@ public final class ChannelRule extends ExternalResource {
         final FastPipedOutputStream p1o = new FastPipedOutputStream(p1i);
         final FastPipedOutputStream p2o = new FastPipedOutputStream(p2i);
 
-        Future<Channel> f1 = executors.submit(new Callable<Channel>() {
+        Future<Channel> f1 = executors.submit(new Callable<>() {
             @Override
             public Channel call() throws Exception {
                 return new ChannelBuilder("This side of the channel", executors).withMode(Channel.Mode.BINARY).build(p1i, p2o);
             }
         });
-        Future<Channel> f2 = executors.submit(new Callable<Channel>() {
+        Future<Channel> f2 = executors.submit(new Callable<>() {
             @Override
             public Channel call() throws Exception {
                 return new ChannelBuilder("The other side of the channel", executors).withMode(Channel.Mode.BINARY).build(p2i, p1o);

core/src/test/java/hudson/cli/ListJobsCommandTest.java

@@ -153,7 +153,7 @@ public class ListJobsCommandTest {
 
     private TypeSafeMatcher<ByteArrayOutputStream> empty() {
 
-        return new TypeSafeMatcher<ByteArrayOutputStream>() {
+        return new TypeSafeMatcher<>() {
 
             @Override
             protected boolean matchesSafely(ByteArrayOutputStream item) {
@@ -178,7 +178,7 @@ public class ListJobsCommandTest {
 
     private TypeSafeMatcher<ByteArrayOutputStream> listsJobs(final String... expected) {
 
-        return new TypeSafeMatcher<ByteArrayOutputStream>() {
+        return new TypeSafeMatcher<>() {
 
             @Override
             protected boolean matchesSafely(ByteArrayOutputStream item) {

core/src/test/java/hudson/util/DescribableListTest.java

@@ -69,7 +69,7 @@ public class DescribableListTest {
 
         @Override
         public Descriptor<Datum> getDescriptor() {
-            return new Descriptor<Datum>(Datum.class) {};
+            return new Descriptor<>(Datum.class) {};
         }
 
         @Override