Fix checkstyle issues

pgpainless-core/src/main/java/org/pgpainless/key/generation/KeyRingBuilder.java

@@ -26,7 +26,6 @@ import java.util.Date;
 import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.List;
-import java.util.Objects;
 import java.util.Set;
 import javax.annotation.Nonnull;
 
@@ -53,6 +52,7 @@ import org.bouncycastle.openpgp.operator.jcajce.JcePBESecretKeyDecryptorBuilder;
 import org.bouncycastle.openpgp.operator.jcajce.JcePBESecretKeyEncryptorBuilder;
 import org.pgpainless.algorithm.HashAlgorithm;
 import org.pgpainless.algorithm.KeyFlag;
+import org.pgpainless.algorithm.SignatureType;
 import org.pgpainless.key.collection.PGPKeyRing;
 import org.pgpainless.key.generation.type.ECDH;
 import org.pgpainless.key.generation.type.ECDSA;
@@ -215,7 +215,7 @@ public class KeyRingBuilder implements KeyRingBuilderInterface {
 
         @Override
         public WithAdditionalUserIdOrPassphrase withAdditionalUserId(@Nonnull String userId) {
-            if (Objects.equals(KeyRingBuilder.this.userId, userId)) {
+            if (KeyRingBuilder.this.userId.equals(userId)) {
                 throw new IllegalArgumentException("Additional user-id MUST NOT be equal to primary user-id.");
             }
             KeyRingBuilder.this.additionalUserIds.add(userId);

pgpainless-core/src/main/java/org/pgpainless/key/generation/KeyRingBuilderInterface.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2018 Paul Schaub.
+ * Copyright 2018-2020 Paul Schaub.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

pgpainless-core/src/test/java/org/pgpainless/key/generation/GenerateKeyWithAdditionalUserIdTest.java

@@ -1,3 +1,18 @@
+/*
+ * Copyright 2018 Paul Schaub.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 package org.pgpainless.key.generation;
 
 import static org.junit.Assert.assertEquals;
@@ -43,6 +58,8 @@ public class GenerateKeyWithAdditionalUserIdTest {
         armor.close();
 
         // echo this | gpg --list-packets
+        // CHECKSTYLE:OFF
         System.out.println(byteOut.toString("UTF-8"));
+        // CHECKSTYLE:ON
     }
 }