Some small improvements (#11564)

Signed-off-by: xingrufei <[email protected]>

Author: skyguard1

codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2LocalFlowController.java

@@ -410,7 +410,7 @@ public void incrementFlowControlWindows(int delta) throws Http2Exception {
 
             window += delta;
             processedWindow += delta;
-            lowerBound = delta < 0 ? delta : 0;
+            lowerBound = Math.min(delta, 0);
         }
 
         @Override

codec-http2/src/main/java/io/netty/handler/codec/http2/Http2ServerUpgradeCodec.java

@@ -128,7 +128,7 @@ public boolean prepareUpgradeResponse(ChannelHandlerContext ctx, FullHttpRequest
             // Decode the HTTP2-Settings header and set the settings on the handler to make
             // sure everything is fine with the request.
             List<String> upgradeHeaders = upgradeRequest.headers().getAll(HTTP_UPGRADE_SETTINGS_HEADER);
-            if (upgradeHeaders.isEmpty() || upgradeHeaders.size() > 1) {
+            if (upgradeHeaders.size() != 1) {
                 throw new IllegalArgumentException("There must be 1 and only 1 "
                         + HTTP_UPGRADE_SETTINGS_HEADER + " header.");
             }

resolver/src/main/java/io/netty/resolver/HostsFileParser.java

@@ -111,7 +111,7 @@ private static HostsFileEntries hostsFileEntries(HostsFileEntriesProvider provid
     }
 
     private static Map<String, ?> toMapWithSingleValue(Map<String, List<InetAddress>> fromMapWithListValue) {
-        Map<String, InetAddress> result = new HashMap<String, InetAddress>();
+        Map<String, InetAddress> result = new HashMap<String, InetAddress>(fromMapWithListValue.size());
         for (Map.Entry<String, List<InetAddress>> entry : fromMapWithListValue.entrySet()) {
             List<InetAddress> value = entry.getValue();
             if (!value.isEmpty()) {