Add "unsed import" check.

benchmarks/src/main/java/io/grpc/benchmarks/qps/QpsClient.java

@@ -38,7 +38,6 @@ import static io.grpc.testing.integration.Util.loadCert;
 import static java.lang.Math.max;
 
 import com.google.common.base.Preconditions;
-import com.google.common.util.concurrent.MoreExecutors;
 
 import grpc.testing.Qpstest.PayloadType;
 import grpc.testing.TestServiceGrpc;
@@ -58,7 +57,6 @@ import java.io.IOException;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.util.ArrayList;
-import java.util.IllegalFormatException;
 import java.util.List;
 import java.util.concurrent.CancellationException;
 import java.util.concurrent.ExecutionException;

benchmarks/src/main/java/io/grpc/benchmarks/qps/QpsServer.java

@@ -45,9 +45,7 @@ import static grpc.testing.Qpstest.StreamingOutputCallRequest;
 import static grpc.testing.Qpstest.StreamingOutputCallResponse;
 import static io.grpc.testing.integration.Util.loadCert;
 import static io.grpc.testing.integration.Util.pickUnusedPort;
-import static java.lang.Math.max;
 
-import com.google.common.util.concurrent.MoreExecutors;
 import com.google.protobuf.ByteString;
 
 import grpc.testing.Qpstest;
@@ -56,8 +54,6 @@ import io.grpc.ServerImpl;
 import io.grpc.Status;
 import io.grpc.stub.StreamObserver;
 import io.grpc.transport.netty.NettyServerBuilder;
-import io.netty.channel.EventLoopGroup;
-import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.handler.ssl.SslContext;
 
 import java.io.File;

checkstyle.xml

@@ -49,6 +49,7 @@
             <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
         </module>
         <module name="AvoidStarImport"/>
+        <module name="UnusedImports"/>
         <module name="OneTopLevelClass"/>
         <module name="NoLineWrap"/>
         <module name="EmptyBlock">

core/src/test/java/io/grpc/transport/MessageFramerTest.java

@@ -38,8 +38,6 @@ import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 
-import com.google.common.base.Preconditions;
-
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;

integration-testing/src/main/java/io/grpc/testing/integration/AbstractTransportTest.java

@@ -71,9 +71,7 @@ import org.junit.Before;
 import org.junit.Test;
 import org.mockito.ArgumentCaptor;
 
-import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.Executors;

integration-testing/src/main/java/io/grpc/testing/integration/TestServiceClient.java

@@ -37,13 +37,10 @@ import io.grpc.transport.netty.NettyChannelBuilder;
 import io.grpc.transport.okhttp.OkHttpChannelBuilder;
 import io.netty.handler.ssl.SslContext;
 
-import java.io.File;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.UnknownHostException;
 
-import javax.net.ssl.SSLException;
-
 /**
  * Application that starts a client for the {@link TestServiceGrpc.TestService} and runs through a
  * series of tests.

integration-testing/src/main/java/io/grpc/testing/integration/TestServiceImpl.java

@@ -36,7 +36,6 @@ import com.google.protobuf.ByteString;
 import com.google.protobuf.EmptyProtos;
 
 import io.grpc.stub.StreamObserver;
-import io.grpc.testing.integration.Messages.Payload;
 import io.grpc.testing.integration.Messages.PayloadType;
 import io.grpc.testing.integration.Messages.ResponseParameters;
 import io.grpc.testing.integration.Messages.SimpleRequest;

integration-testing/src/main/java/io/grpc/testing/integration/TestServiceServer.java

@@ -39,7 +39,6 @@ import io.grpc.testing.TestUtils;
 import io.grpc.transport.netty.NettyServerBuilder;
 import io.netty.handler.ssl.SslContext;
 
-import java.io.File;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;

integration-testing/src/main/java/io/grpc/testing/integration/Util.java

@@ -40,7 +40,6 @@ import org.junit.Assert;
 
 import java.io.BufferedWriter;
 import java.io.File;
-import java.io.FileOutputStream;
 import java.io.FileWriter;
 import java.io.InputStream;
 import java.io.IOException;

integration-testing/src/test/java/io/grpc/testing/integration/Http2NettyTest.java

@@ -32,7 +32,6 @@
 package io.grpc.testing.integration;
 
 import io.grpc.ChannelImpl;
-import io.grpc.transport.netty.NegotiationType;
 import io.grpc.transport.netty.NettyChannelBuilder;
 import io.grpc.transport.netty.NettyServerBuilder;
 import io.netty.handler.ssl.SslContext;

netty/src/main/java/io/grpc/transport/netty/NettyServerBuilder.java

@@ -37,7 +37,6 @@ import com.google.common.util.concurrent.Service;
 
 import io.grpc.AbstractServerBuilder;
 import io.grpc.HandlerRegistry;
-import io.grpc.ServerImpl;
 import io.grpc.SharedResourceHolder;
 import io.grpc.transport.ServerListener;
 import io.netty.channel.EventLoopGroup;

stub/src/main/java/io/grpc/stub/Calls.java

@@ -47,7 +47,6 @@ import java.util.Iterator;
 import java.util.NoSuchElementException;
 import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.BlockingQueue;
-import java.util.concurrent.CancellationException;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;