diff --git a/pgpainless-core/src/main/java/org/pgpainless/decryption_verification/SignatureVerifyingInputStream.java b/pgpainless-core/src/main/java/org/pgpainless/decryption_verification/SignatureVerifyingInputStream.java
index d5f4c891..ab2f22b5 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/decryption_verification/SignatureVerifyingInputStream.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/decryption_verification/SignatureVerifyingInputStream.java
@@ -179,12 +179,12 @@ public class SignatureVerifyingInputStream extends FilterInputStream {
     }
 
     @Override
-    public int read(byte[] b) throws IOException {
+    public int read(@Nonnull byte[] b) throws IOException {
         return read(b, 0, b.length);
     }
 
     @Override
-    public int read(byte[] b, int off, int len) throws IOException {
+    public int read(@Nonnull byte[] b, int off, int len) throws IOException {
         int read = super.read(b, off, len);
 
         final boolean endOfStream = read == -1;
diff --git a/pgpainless-core/src/main/java/org/pgpainless/key/modification/secretkeyring/SecretKeyRingEditor.java b/pgpainless-core/src/main/java/org/pgpainless/key/modification/secretkeyring/SecretKeyRingEditor.java
index 3d1b9670..ee8fca9f 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/key/modification/secretkeyring/SecretKeyRingEditor.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/key/modification/secretkeyring/SecretKeyRingEditor.java
@@ -342,10 +342,7 @@ public class SecretKeyRingEditor implements SecretKeyRingEditorInterface {
         }
 
         boolean found = false;
-        Iterator<PGPSecretKey> iterator = secretKeyRing.iterator();
-        while (iterator.hasNext()) {
-            PGPSecretKey secretKey = iterator.next();
-
+        for (PGPSecretKey secretKey : secretKeyRing) {
             // Skip over unaffected subkeys
             if (secretKey.getKeyID() != fingerprint.getKeyId()) {
                 secretKeyList.add(secretKey);
diff --git a/pgpainless-core/src/main/java/org/pgpainless/key/util/UserId.java b/pgpainless-core/src/main/java/org/pgpainless/key/util/UserId.java
index dc232b8c..eae331fc 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/key/util/UserId.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/key/util/UserId.java
@@ -16,6 +16,8 @@
 
 package org.pgpainless.key.util;
 
+import javax.annotation.Nonnull;
+
 public final class UserId implements CharSequence {
     public static final class Builder {
         private String name;
@@ -127,7 +129,7 @@ public final class UserId implements CharSequence {
     }
 
     @Override
-    public String toString() {
+    public @Nonnull String toString() {
         return asString(false);
     }
 
diff --git a/pgpainless-core/src/main/java/org/pgpainless/util/CollectionUtils.java b/pgpainless-core/src/main/java/org/pgpainless/util/CollectionUtils.java
index bd618e4e..bf687229 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/util/CollectionUtils.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/util/CollectionUtils.java
@@ -24,8 +24,8 @@ public class CollectionUtils {
     public static <I> List<I> iteratorToList(Iterator<I> iterator) {
         List<I> items = new ArrayList<>();
         while (iterator.hasNext()) {
-            Object o = iterator.next();
-            items.add((I) o);
+            I item = iterator.next();
+            items.add(item);
         }
         return items;
     }
diff --git a/pgpainless-core/src/test/java/org/bouncycastle/PGPPublicKeyRingTest.java b/pgpainless-core/src/test/java/org/bouncycastle/PGPPublicKeyRingTest.java
index 216c8bb7..6cf8d237 100644
--- a/pgpainless-core/src/test/java/org/bouncycastle/PGPPublicKeyRingTest.java
+++ b/pgpainless-core/src/test/java/org/bouncycastle/PGPPublicKeyRingTest.java
@@ -40,10 +40,6 @@ public class PGPPublicKeyRingTest {
      * It does not.
      *
      * see also https://security.stackexchange.com/questions/92635/is-it-possible-to-assign-different-uids-to-subkeys-for-the-purpose-of-having-mul
-     *
-     * @throws InvalidAlgorithmParameterException
-     * @throws NoSuchAlgorithmException
-     * @throws PGPException
      */
     @Test
     public void subkeysDoNotHaveUserIDsTest() throws InvalidAlgorithmParameterException, NoSuchAlgorithmException, PGPException {
@@ -54,10 +50,8 @@ public class PGPPublicKeyRingTest {
             Iterator<String> userIds = subkey.getUserIDs();
             if (primaryKey == subkey) {
                 assertEquals("primary@user.id", userIds.next());
-                assertFalse(userIds.hasNext());
-            } else {
-                assertFalse(userIds.hasNext());
             }
+            assertFalse(userIds.hasNext());
         }
     }
 
diff --git a/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/ModificationDetectionTests.java b/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/ModificationDetectionTests.java
index aa1938d1..a9b92750 100644
--- a/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/ModificationDetectionTests.java
+++ b/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/ModificationDetectionTests.java
@@ -126,9 +126,9 @@ public class ModificationDetectionTests {
 
     /**
      * Messages containing a missing MDC shall fail to decrypt.
-     * @param implementationFactory
-     * @throws IOException
-     * @throws PGPException
+     * @param implementationFactory implementation factory
+     * @throws IOException in case of an io-error
+     * @throws PGPException in case of a pgp error
      */
     @ParameterizedTest
     @MethodSource("org.pgpainless.util.TestUtil#provideImplementationFactories")
diff --git a/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/RecursionDepthTest.java b/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/RecursionDepthTest.java
index 30f8b609..74dfa22f 100644
--- a/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/RecursionDepthTest.java
+++ b/pgpainless-core/src/test/java/org/pgpainless/decryption_verification/RecursionDepthTest.java
@@ -39,8 +39,6 @@ public class RecursionDepthTest {
      * Test that decryption is aborted when maximum recursion depth of nested packets is exceeded.
      *
      * @see <a href="https://tests.sequoia-pgp.org/#Maximum_recursion_depth">Sequoia-PGP Test Suite</a>
-     * @throws IOException
-     * @throws PGPException
      */
     @ParameterizedTest
     @MethodSource("org.pgpainless.util.TestUtil#provideImplementationFactories")
diff --git a/pgpainless-core/src/test/java/org/pgpainless/provider/ProviderFactoryTest.java b/pgpainless-core/src/test/java/org/pgpainless/provider/ProviderFactoryTest.java
index d815d68d..be642344 100644
--- a/pgpainless-core/src/test/java/org/pgpainless/provider/ProviderFactoryTest.java
+++ b/pgpainless-core/src/test/java/org/pgpainless/provider/ProviderFactoryTest.java
@@ -38,6 +38,7 @@ public class ProviderFactoryTest {
 
     private ProviderFactory customProviderFactory = new ProviderFactory() {
 
+        @SuppressWarnings("deprecation")
         Provider provider = new Provider("PL", 1L, "PGPainlessTestProvider") {
 
         };