Enable new errorprone checks and fix violations (#3018)

proxy/src/main/java/google/registry/proxy/handler/ProxyProtocolHandler.java

@@ -114,8 +114,8 @@ public class ProxyProtocolHandler extends ByteToMessageDecoder {
 
   private static String getSourceIP(ChannelHandlerContext ctx) {
     SocketAddress remoteAddress = ctx.channel().remoteAddress();
-    return (remoteAddress instanceof InetSocketAddress)
-        ? ((InetSocketAddress) remoteAddress).getAddress().getHostAddress()
+    return (remoteAddress instanceof InetSocketAddress inetSocketAddress)
+        ? inetSocketAddress.getAddress().getHostAddress()
         : null;
   }
 

proxy/src/main/java/google/registry/proxy/handler/RelayHandler.java

@@ -93,8 +93,8 @@ public class RelayHandler<I> extends SimpleChannelInboundHandler<I> {
     // to zero and its buffer will be freed. After the buffer is freed, the message cannot be used
     // anymore, even if in Java's eye the object still exist, its content is gone. We increment a
     // count here so that the message can be retried, in case the relay is not successful.
-    if (msg instanceof ReferenceCounted) {
-      ((ReferenceCounted) msg).retain();
+    if (msg instanceof ReferenceCounted referenceCounted) {
+      referenceCounted.retain();
     }
     ChannelFuture unusedFuture =
         relayChannel

proxy/src/test/java/google/registry/proxy/TestUtils.java

@@ -150,8 +150,8 @@ public final class TestUtils {
   private static void assertHttpMessageEquivalent(HttpMessage msg1, HttpMessage msg2) {
     assertThat(msg1.protocolVersion()).isEqualTo(msg2.protocolVersion());
     assertThat(msg1.headers()).isEqualTo(msg2.headers());
-    if (msg1 instanceof FullHttpRequest && msg2 instanceof FullHttpRequest) {
-      assertThat(((FullHttpRequest) msg1).content()).isEqualTo(((FullHttpRequest) msg2).content());
+    if (msg1 instanceof FullHttpRequest req1 && msg2 instanceof FullHttpRequest req2) {
+      assertThat(req1.content()).isEqualTo(req2.content());
     }
   }
 

proxy/src/test/java/google/registry/proxy/quota/TokenStoreTest.java

@@ -302,8 +302,7 @@ class TokenStoreTest {
     // Verify that a task is scheduled.
     ArgumentCaptor<Runnable> argument = ArgumentCaptor.forClass(Runnable.class);
     verify(refreshExecutor)
-        .scheduleWithFixedDelay(
-            argument.capture(), eq((long) 5), eq((long) 5), eq(TimeUnit.SECONDS));
+        .scheduleWithFixedDelay(argument.capture(), eq(5L), eq(5L), eq(TimeUnit.SECONDS));
 
     // Verify that the scheduled task calls TokenStore.refresh().
     argument.getValue().run();