IDE warnings cleanup (#8768)

Motivation:

IDE shows some warnings

Modification:

Small IDE warnings cleanup in different places.

Result:

Less warnings

buffer/src/main/java/io/netty/buffer/PoolArena.java

@@ -461,13 +461,10 @@ abstract class PoolArena<T> implements PoolArenaMetric {
                 continue;
             }
             PoolSubpage<?> s = head.next;
-            for (;;) {
+            do {
                 metrics.add(s);
                 s = s.next;
-                if (s == head) {
-                    break;
-                }
-            }
+            } while (s != head);
         }
         return metrics;
     }
@@ -631,13 +628,10 @@ abstract class PoolArena<T> implements PoolArenaMetric {
                     .append(i)
                     .append(": ");
             PoolSubpage<?> s = head.next;
-            for (;;) {
+            do {
                 buf.append(s);
                 s = s.next;
-                if (s == head) {
-                    break;
-                }
-            }
+            } while (s != head);
         }
     }
 

codec-http2/src/main/java/io/netty/handler/codec/http2/Http2Exception.java

@@ -194,7 +194,7 @@ public class Http2Exception extends Exception {
     /**
      * Provides a hint as to if shutdown is justified, what type of shutdown should be executed.
      */
-    public static enum ShutdownHint {
+    public enum ShutdownHint {
         /**
          * Do not shutdown the underlying channel.
          */
@@ -207,7 +207,7 @@ public class Http2Exception extends Exception {
         /**
          * Close the channel immediately after a {@code GOAWAY} is sent.
          */
-        HARD_SHUTDOWN;
+        HARD_SHUTDOWN
     }
 
     /**

codec-smtp/src/main/java/io/netty/handler/codec/smtp/SmtpRequests.java

@@ -20,6 +20,7 @@ import io.netty.util.internal.ObjectUtil;
 import io.netty.util.internal.UnstableApi;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -94,9 +95,7 @@ public final class SmtpRequests {
         } else {
             List<CharSequence> params = new ArrayList<>(mailParameters.length + 1);
             params.add(sender != null? "FROM:<" + sender + '>' : FROM_NULL_SENDER);
-            for (CharSequence param : mailParameters) {
-                params.add(param);
-            }
+            Collections.addAll(params, mailParameters);
             return new DefaultSmtpRequest(SmtpCommand.MAIL, params);
         }
     }
@@ -111,9 +110,7 @@ public final class SmtpRequests {
         } else {
             List<CharSequence> params = new ArrayList<>(rcptParameters.length + 1);
             params.add("TO:<" + recipient + '>');
-            for (CharSequence param : rcptParameters) {
-                params.add(param);
-            }
+            Collections.addAll(params, rcptParameters);
             return new DefaultSmtpRequest(SmtpCommand.RCPT, params);
         }
     }

handler/src/main/java/io/netty/handler/ssl/JdkSslContext.java

@@ -101,9 +101,7 @@ public class JdkSslContext extends SslContext {
         // Choose the sensible default list of protocols.
         final String[] supportedProtocols = engine.getSupportedProtocols();
         Set<String> supportedProtocolsSet = new HashSet<>(supportedProtocols.length);
-        for (int i = 0; i < supportedProtocols.length; ++i) {
-            supportedProtocolsSet.add(supportedProtocols[i]);
-        }
+        Collections.addAll(supportedProtocolsSet, supportedProtocols);
         List<String> protocols = new ArrayList<>();
         addIfSupported(
                 supportedProtocolsSet, protocols,

handler/src/main/java/io/netty/handler/ssl/PemReader.java

@@ -81,10 +81,7 @@ final class PemReader {
         List<ByteBuf> certs = new ArrayList<>();
         Matcher m = CERT_PATTERN.matcher(content);
         int start = 0;
-        for (;;) {
-            if (!m.find(start)) {
-                break;
-            }
+        while (m.find(start)) {
 
             ByteBuf base64 = Unpooled.copiedBuffer(m.group(1), CharsetUtil.US_ASCII);
             ByteBuf der = Base64.decode(base64);

handler/src/main/java/io/netty/handler/ssl/SslUtils.java

@@ -122,9 +122,7 @@ final class SslUtils {
         // AES256 requires JCE unlimited strength jurisdiction policy files.
         defaultCiphers.add("TLS_RSA_WITH_AES_256_CBC_SHA");
 
-        for (String tlsv13Cipher: DEFAULT_TLSV13_CIPHER_SUITES) {
-            defaultCiphers.add(tlsv13Cipher);
-        }
+        Collections.addAll(defaultCiphers, DEFAULT_TLSV13_CIPHER_SUITES);
 
         DEFAULT_CIPHER_SUITES = defaultCiphers.toArray(new String[0]);
     }

testsuite/src/main/java/io/netty/testsuite/transport/socket/SocketMultipleConnectTest.java

@@ -61,12 +61,6 @@ public class SocketMultipleConnectTest extends AbstractSocketTest {
 
     @Override
     protected List<TestsuitePermutation.BootstrapComboFactory<ServerBootstrap, Bootstrap>> newFactories() {
-        List<TestsuitePermutation.BootstrapComboFactory<ServerBootstrap, Bootstrap>> factories
-                = new ArrayList<>();
-        for (TestsuitePermutation.BootstrapComboFactory<ServerBootstrap, Bootstrap> comboFactory
-                : SocketTestPermutation.INSTANCE.socket()) {
-            factories.add(comboFactory);
-        }
-        return factories;
+        return new ArrayList<>(SocketTestPermutation.INSTANCE.socket());
     }
 }