diff --git a/core/src/main/java/hudson/Functions.java b/core/src/main/java/hudson/Functions.java
index 6756715726..d49e49a358 100644
--- a/core/src/main/java/hudson/Functions.java
+++ b/core/src/main/java/hudson/Functions.java
@@ -1685,7 +1685,7 @@ public class Functions {
         if (Util.isOverridden(Throwable.class, t.getClass(), "printStackTrace", PrintWriter.class)) {
             StringWriter sw = new StringWriter();
             t.printStackTrace(new PrintWriter(sw));
-            s.append(sw.toString());
+            s.append(sw);
             return;
         }
         Throwable lower = t.getCause();
diff --git a/core/src/main/java/hudson/Launcher.java b/core/src/main/java/hudson/Launcher.java
index 9baa3992fa..3bc5f5ca51 100644
--- a/core/src/main/java/hudson/Launcher.java
+++ b/core/src/main/java/hudson/Launcher.java
@@ -813,7 +813,7 @@ public abstract class Launcher {
             } else
                 buf.append(c);
         }
-        listener.getLogger().println(buf.toString());
+        listener.getLogger().println(buf);
         listener.getLogger().flush();
     }
 
diff --git a/core/src/main/java/hudson/WebAppMain.java b/core/src/main/java/hudson/WebAppMain.java
index 6eab71e566..1f88bae7cb 100644
--- a/core/src/main/java/hudson/WebAppMain.java
+++ b/core/src/main/java/hudson/WebAppMain.java
@@ -341,7 +341,7 @@ public class WebAppMain implements ServletContextListener {
      */
     private void recordBootAttempt(File home) {
         try (OutputStream o=Files.newOutputStream(BootFailure.getBootFailureFile(home).toPath(), StandardOpenOption.CREATE, StandardOpenOption.APPEND)) {
-            o.write((new Date().toString() + System.getProperty("line.separator", "\n")).getBytes());
+            o.write((new Date() + System.getProperty("line.separator", "\n")).getBytes());
         } catch (IOException | InvalidPathException e) {
             LOGGER.log(WARNING, "Failed to record boot attempts",e);
         }
diff --git a/core/src/main/java/hudson/diagnosis/OldDataMonitor.java b/core/src/main/java/hudson/diagnosis/OldDataMonitor.java
index 6345dff0c5..fa43d35890 100644
--- a/core/src/main/java/hudson/diagnosis/OldDataMonitor.java
+++ b/core/src/main/java/hudson/diagnosis/OldDataMonitor.java
@@ -274,7 +274,7 @@ public class OldDataMonitor extends AdministrativeMonitor {
 
         @Override
         public String toString() {
-            return min==null ? "" : min.toString() + (single ? "" : " - " + max.toString());
+            return min==null ? "" : min + (single ? "" : " - " + max.toString());
         }
 
         /**
diff --git a/core/src/main/java/hudson/init/TaskMethodFinder.java b/core/src/main/java/hudson/init/TaskMethodFinder.java
index c23aa88f76..06702e4ea8 100644
--- a/core/src/main/java/hudson/init/TaskMethodFinder.java
+++ b/core/src/main/java/hudson/init/TaskMethodFinder.java
@@ -84,7 +84,7 @@ abstract class TaskMethodFinder<T extends Annotation> extends TaskBuilder {
                     c.getClassLoader().loadClass(c.getPackage().getName() + ".Messages"));
             return rb.format(key);
         } catch (ClassNotFoundException x) {
-            LOGGER.log(WARNING, "Failed to load "+x.getMessage()+" for "+e.toString(),x);
+            LOGGER.log(WARNING, "Failed to load "+x.getMessage()+" for "+ e,x);
             return key;
         } catch (MissingResourceException x) {
             LOGGER.log(WARNING, "Could not find key '" + key + "' in " + c.getPackage().getName() + ".Messages", x);
diff --git a/core/src/main/java/hudson/init/impl/InstallUncaughtExceptionHandler.java b/core/src/main/java/hudson/init/impl/InstallUncaughtExceptionHandler.java
index 2eaec5326f..4241d5a5e8 100644
--- a/core/src/main/java/hudson/init/impl/InstallUncaughtExceptionHandler.java
+++ b/core/src/main/java/hudson/init/impl/InstallUncaughtExceptionHandler.java
@@ -32,9 +32,7 @@ public class InstallUncaughtExceptionHandler {
 
     @Initializer
     public static void init(final Jenkins j) throws IOException {
-        CompressionFilter.setUncaughtExceptionHandler(j.servletContext, (e, context, req, rsp) -> {
-            handleException(j, e, req, rsp, 500);
-        });
+        CompressionFilter.setUncaughtExceptionHandler(j.servletContext, (e, context, req, rsp) -> handleException(j, e, req, rsp, 500));
         try {
             Thread.setDefaultUncaughtExceptionHandler(new DefaultUncaughtExceptionHandler());
             LOGGER.log(Level.FINE, "Successfully installed a global UncaughtExceptionHandler.");
diff --git a/core/src/main/java/hudson/model/Executor.java b/core/src/main/java/hudson/model/Executor.java
index 3587ad904b..9e7cfc0499 100644
--- a/core/src/main/java/hudson/model/Executor.java
+++ b/core/src/main/java/hudson/model/Executor.java
@@ -417,7 +417,7 @@ public class Executor extends Thread implements ModelObject {
                     }
                 }
 
-                setName(getName() + " : executing " + executable.toString());
+                setName(getName() + " : executing " + executable);
                 Authentication auth = workUnit.context.item.authenticate2();
                 LOGGER.log(FINE, "{0} is now executing {1} as {2}", new Object[] {getName(), executable, auth});
                 if (LOGGER.isLoggable(FINE) && auth.equals(ACL.SYSTEM2)) { // i.e., unspecified
diff --git a/core/src/main/java/hudson/scm/ChangeLogSet.java b/core/src/main/java/hudson/scm/ChangeLogSet.java
index 135869989b..c78edcba8d 100644
--- a/core/src/main/java/hudson/scm/ChangeLogSet.java
+++ b/core/src/main/java/hudson/scm/ChangeLogSet.java
@@ -253,7 +253,7 @@ public abstract class ChangeLogSet<T extends ChangeLogSet.Entry> implements Iter
                 } catch(Exception e) {
                     LOGGER.info("ChangeLogAnnotator " + a.toString() + " failed to annotate message '" + getMsg() + "'; " + e.getMessage());
                 } catch(Error e) {
-                    LOGGER.severe("ChangeLogAnnotator " + a.toString() + " failed to annotate message '" + getMsg() + "'; " + e.getMessage());
+                    LOGGER.severe("ChangeLogAnnotator " + a + " failed to annotate message '" + getMsg() + "'; " + e.getMessage());
                 }
 
             return markup.toString(false);
diff --git a/core/src/main/java/hudson/util/FormFieldValidator.java b/core/src/main/java/hudson/util/FormFieldValidator.java
index f3e78b1292..eab40cb382 100644
--- a/core/src/main/java/hudson/util/FormFieldValidator.java
+++ b/core/src/main/java/hudson/util/FormFieldValidator.java
@@ -567,10 +567,8 @@ public abstract class FormFieldValidator {
                 public void validate(File fexe) {
                     try {
                         self.checkExecutable(fexe);
-                    } catch (IOException ioe) {
+                    } catch (IOException | ServletException ioe) {
                         exceptions[0] = ioe;
-                    } catch (ServletException se) {
-                        exceptions[0] = se;
                     }
                 }
             });
diff --git a/core/src/main/java/hudson/util/SecretRewriter.java b/core/src/main/java/hudson/util/SecretRewriter.java
index ffb417a781..0122503366 100644
--- a/core/src/main/java/hudson/util/SecretRewriter.java
+++ b/core/src/main/java/hudson/util/SecretRewriter.java
@@ -110,7 +110,7 @@ public class SecretRewriter {
                         copied = eidx;
                     }
                     buf.append(line.substring(copied));
-                    out.println(buf.toString());
+                    out.println(buf);
                 }
             }
 
diff --git a/core/src/main/java/jenkins/fingerprints/FingerprintStorage.java b/core/src/main/java/jenkins/fingerprints/FingerprintStorage.java
index d92bbf4c22..f447ed378e 100644
--- a/core/src/main/java/jenkins/fingerprints/FingerprintStorage.java
+++ b/core/src/main/java/jenkins/fingerprints/FingerprintStorage.java
@@ -114,7 +114,7 @@ public abstract class FingerprintStorage extends AbstractDescribableImpl<Fingerp
     public boolean cleanFingerprint(@NonNull Fingerprint fingerprint, TaskListener taskListener) {
         try {
             if (!fingerprint.isAlive() && fingerprint.getFacetBlockingDeletion() == null) {
-                taskListener.getLogger().println("deleting obsolete " + fingerprint.toString());
+                taskListener.getLogger().println("deleting obsolete " + fingerprint);
                 Fingerprint.delete(fingerprint.getHashString());
                 return true;
             } else {
diff --git a/core/src/main/java/jenkins/model/identity/IdentityRootAction.java b/core/src/main/java/jenkins/model/identity/IdentityRootAction.java
index 50a0862548..fdfee1cc79 100644
--- a/core/src/main/java/jenkins/model/identity/IdentityRootAction.java
+++ b/core/src/main/java/jenkins/model/identity/IdentityRootAction.java
@@ -52,7 +52,7 @@ public class IdentityRootAction implements UnprotectedRootAction {
             buf.append(new String(encoded, index, len, StandardCharsets.UTF_8));
             index += len;
         }
-        return String.format("-----BEGIN PUBLIC KEY-----%n%s%n-----END PUBLIC KEY-----%n", buf.toString());
+        return String.format("-----BEGIN PUBLIC KEY-----%n%s%n-----END PUBLIC KEY-----%n", buf);
     }
 
     /**
diff --git a/core/src/main/java/jenkins/util/JSONSignatureValidator.java b/core/src/main/java/jenkins/util/JSONSignatureValidator.java
index b696a3f3af..1dcd433f42 100644
--- a/core/src/main/java/jenkins/util/JSONSignatureValidator.java
+++ b/core/src/main/java/jenkins/util/JSONSignatureValidator.java
@@ -73,9 +73,9 @@ public class JSONSignatureValidator {
                         try {
                             c.checkValidity();
                         } catch (CertificateExpiredException e) { // even if the certificate isn't valid yet, we'll proceed it anyway
-                            warning = FormValidation.warning(e, String.format("Certificate %s has expired in %s", cert.toString(), name));
+                            warning = FormValidation.warning(e, String.format("Certificate %s has expired in %s", cert, name));
                         } catch (CertificateNotYetValidException e) {
-                            warning = FormValidation.warning(e, String.format("Certificate %s is not yet valid in %s", cert.toString(), name));
+                            warning = FormValidation.warning(e, String.format("Certificate %s is not yet valid in %s", cert, name));
                         }
                         LOGGER.log(Level.FINE, "Add certificate found in JSON document:\n\tsubjectDN: {0}\n\tissuer: {1}\n\tnotBefore: {2}\n\tnotAfter: {3}",
                                 new Object[] { c.getSubjectDN(), c.getIssuerDN(), c.getNotBefore(), c.getNotAfter() });
diff --git a/core/src/main/java/jenkins/util/ResourceBundleUtil.java b/core/src/main/java/jenkins/util/ResourceBundleUtil.java
index 7a53b54785..60b71ae696 100644
--- a/core/src/main/java/jenkins/util/ResourceBundleUtil.java
+++ b/core/src/main/java/jenkins/util/ResourceBundleUtil.java
@@ -70,7 +70,7 @@ public class ResourceBundleUtil {
      * @throws MissingResourceException Missing resource bundle.
      */
     public static @NonNull JSONObject getBundle(@NonNull String baseName, @NonNull Locale locale) throws MissingResourceException {
-        String bundleKey = baseName + ":" + locale.toString();
+        String bundleKey = baseName + ":" + locale;
         JSONObject bundleJSON = bundles.get(bundleKey);
 
         if (bundleJSON != null) {
diff --git a/core/src/test/java/hudson/UtilTest.java b/core/src/test/java/hudson/UtilTest.java
index 2222543c0f..9ab683838c 100644
--- a/core/src/test/java/hudson/UtilTest.java
+++ b/core/src/test/java/hudson/UtilTest.java
@@ -599,9 +599,7 @@ public class UtilTest {
 
     @Test
     public void ifOverriddenFailure() {
-        AbstractMethodError error = Assert.assertThrows(AbstractMethodError.class, () -> {
-            Util.ifOverridden(() -> true, BaseClass.class, DerivedClassFailure.class, "method");
-        });
+        AbstractMethodError error = Assert.assertThrows(AbstractMethodError.class, () -> Util.ifOverridden(() -> true, BaseClass.class, DerivedClassFailure.class, "method"));
         assertEquals("The class " + DerivedClassFailure.class.getName() + " must override at least one of the BaseClass.method methods", error.getMessage());
     }
 
diff --git a/core/src/test/java/hudson/XmlFileTest.java b/core/src/test/java/hudson/XmlFileTest.java
index c8d8b9f3c1..e208c48440 100644
--- a/core/src/test/java/hudson/XmlFileTest.java
+++ b/core/src/test/java/hudson/XmlFileTest.java
@@ -42,7 +42,7 @@ public class XmlFileTest {
 
         XmlFile xmlFile =  new XmlFile(xs, new File(configUrl.getFile()));
         if (xmlFile.exists()) {
-            assertThrows(SAXParseException.class, () -> xmlFile.read());
+            assertThrows(SAXParseException.class, xmlFile::read);
         }
     }
 
diff --git a/core/src/test/java/jenkins/RemotingJarSignatureTest.java b/core/src/test/java/jenkins/RemotingJarSignatureTest.java
index f054d6b170..f6103ec165 100644
--- a/core/src/test/java/jenkins/RemotingJarSignatureTest.java
+++ b/core/src/test/java/jenkins/RemotingJarSignatureTest.java
@@ -1,7 +1,6 @@
 package jenkins;
 
 import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.fail;
 
 import hudson.remoting.Channel;
 import hudson.remoting.Which;
diff --git a/core/src/test/java/jenkins/util/JenkinsJVMTest.java b/core/src/test/java/jenkins/util/JenkinsJVMTest.java
index 206ca39fe2..888c592739 100644
--- a/core/src/test/java/jenkins/util/JenkinsJVMTest.java
+++ b/core/src/test/java/jenkins/util/JenkinsJVMTest.java
@@ -13,14 +13,14 @@ public class JenkinsJVMTest {
 
     @Test
     public void checkJenkinsJVM_WhenNotInAJenkinsJVM() {
-        assertThrows(IllegalStateException.class, () -> JenkinsJVM.checkJenkinsJVM());
+        assertThrows(IllegalStateException.class, JenkinsJVM::checkJenkinsJVM);
     }
 
     @Test
     public void checkNotJenkinsJVM_WhenInAJenkinsJVM() {
         JenkinsJVM.setJenkinsJVM(true);
         try {
-            assertThrows(IllegalStateException.class, () -> JenkinsJVM.checkNotJenkinsJVM());
+            assertThrows(IllegalStateException.class, JenkinsJVM::checkNotJenkinsJVM);
         } finally {
             JenkinsJVM.setJenkinsJVM(false);
         }
diff --git a/core/src/test/java/jenkins/util/VirtualFileTest.java b/core/src/test/java/jenkins/util/VirtualFileTest.java
index e2f4d81a45..c28a213b1b 100644
--- a/core/src/test/java/jenkins/util/VirtualFileTest.java
+++ b/core/src/test/java/jenkins/util/VirtualFileTest.java
@@ -100,7 +100,7 @@ public class VirtualFileTest {
         VirtualFile hack = root.child("hack");
         assertFalse(hack.isFile());
         assertFalse(hack.exists());
-        assertThrows(FileNotFoundException.class, () -> hack.open());
+        assertThrows(FileNotFoundException.class, hack::open);
     }
 
     @Issue("JENKINS-26810")