Add ServerBootstrap.group() that takes a single group

example/src/main/java/io/netty/example/localecho/LocalEcho.java

@@ -49,7 +49,7 @@ public class LocalEcho {
             // Note that we can use any event loop to ensure certain local channels
             // are handled by the same event loop thread which drives a certain socket channel
             // to reduce the communication latency between socket channels and local channels.
-            sb.group(new LocalEventLoopGroup(), new LocalEventLoopGroup())
+            sb.group(new LocalEventLoopGroup())
               .channel(new LocalServerChannel())
               .localAddress(addr)
               .handler(new ChannelInitializer<LocalServerChannel>() {
@@ -67,7 +67,7 @@ public class LocalEcho {
                   }
               });
 
-            cb.group(new NioEventLoopGroup())
+            cb.group(new NioEventLoopGroup()) // NIO event loops are also OK
               .channel(new LocalChannel())
               .remoteAddress(addr)
               .handler(new ChannelInitializer<LocalChannel>() {

testsuite/src/test/java/io/netty/testsuite/transport/socket/SocketTestPermutation.java

@@ -56,7 +56,7 @@ final class SocketTestPermutation {
             public ServerBootstrap newInstance() {
                 AioEventLoopGroup loop = new AioEventLoopGroup();
                 return new ServerBootstrap().
-                                group(loop, loop).
+                                group(loop).
                                 channel(new AioServerSocketChannel(loop));
             }
         });

transport/src/main/java/io/netty/bootstrap/ServerBootstrap.java

@@ -63,6 +63,18 @@ public class ServerBootstrap {
     private ChannelHandler childHandler;
     private SocketAddress localAddress;
 
+    public ServerBootstrap group(EventLoopGroup group) {
+        if (group == null) {
+            throw new NullPointerException("group");
+        }
+        if (parentGroup != null) {
+            throw new IllegalStateException("parentGroup set already");
+        }
+        parentGroup = group;
+        childGroup = group;
+        return this;
+    }
+
     public ServerBootstrap group(EventLoopGroup parentGroup, EventLoopGroup childGroup) {
         if (parentGroup == null) {
             throw new NullPointerException("parentGroup");

transport/src/test/java/io/netty/channel/local/LocalChannelRegistryTest.java

@@ -47,7 +47,7 @@ public class LocalChannelRegistryTest {
               .remoteAddress(addr)
               .handler(new TestHandler());
 
-            sb.group(new LocalEventLoopGroup(), new LocalEventLoopGroup())
+            sb.group(new LocalEventLoopGroup())
               .channel(new LocalServerChannel())
               .localAddress(addr)
               .childHandler(new ChannelInitializer<LocalChannel>() {

transport/src/test/java/io/netty/channel/local/LocalTransportThreadModelTest.java

@@ -57,7 +57,7 @@ public class LocalTransportThreadModelTest {
     public static void init() {
         // Configure a test server
         sb = new ServerBootstrap();
-        sb.group(new LocalEventLoopGroup(), new LocalEventLoopGroup())
+        sb.group(new LocalEventLoopGroup())
           .channel(new LocalServerChannel())
           .localAddress(LocalAddress.ANY)
           .childHandler(new ChannelInitializer<LocalChannel>() {