diff --git a/core/src/main/java/hudson/FilePath.java b/core/src/main/java/hudson/FilePath.java
index ef4867ea0a..08ace200fe 100644
--- a/core/src/main/java/hudson/FilePath.java
+++ b/core/src/main/java/hudson/FilePath.java
@@ -1197,7 +1197,7 @@ public final class FilePath implements SerializableOnlyOverRemoting {
 
         private final DelegatingCallable<T, IOException> callable;
 
-        public AbstractInterceptorCallableWrapper(DelegatingCallable<T, IOException> callable) {
+        protected AbstractInterceptorCallableWrapper(DelegatingCallable<T, IOException> callable) {
             this.callable = callable;
         }
 
diff --git a/core/src/main/java/hudson/Launcher.java b/core/src/main/java/hudson/Launcher.java
index b14cee5418..85fc42ea5b 100644
--- a/core/src/main/java/hudson/Launcher.java
+++ b/core/src/main/java/hudson/Launcher.java
@@ -97,7 +97,7 @@ public abstract class Launcher {
     @Restricted(Beta.class)
     protected EnvVarsFilterRuleWrapper envVarsFilterRuleWrapper;
 
-    public Launcher(@NonNull TaskListener listener, @CheckForNull VirtualChannel channel) {
+    protected Launcher(@NonNull TaskListener listener, @CheckForNull VirtualChannel channel) {
         this.listener = listener;
         this.channel = channel;
     }
diff --git a/core/src/main/java/hudson/PluginManager.java b/core/src/main/java/hudson/PluginManager.java
index 957f161895..e45bc76ba1 100644
--- a/core/src/main/java/hudson/PluginManager.java
+++ b/core/src/main/java/hudson/PluginManager.java
@@ -351,7 +351,7 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
      */
     private final PluginStrategy strategy;
 
-    public PluginManager(ServletContext context, File rootDir) {
+    protected PluginManager(ServletContext context, File rootDir) {
         this.context = context;
 
         this.rootDir = rootDir;
diff --git a/core/src/main/java/hudson/console/ConsoleAnnotationDescriptor.java b/core/src/main/java/hudson/console/ConsoleAnnotationDescriptor.java
index 1cfbbbfd4f..3f9a17d143 100644
--- a/core/src/main/java/hudson/console/ConsoleAnnotationDescriptor.java
+++ b/core/src/main/java/hudson/console/ConsoleAnnotationDescriptor.java
@@ -42,11 +42,11 @@ import org.kohsuke.stapler.WebMethod;
  * @since 1.349
  */
 public abstract class ConsoleAnnotationDescriptor extends Descriptor<ConsoleNote<?>> implements ExtensionPoint {
-    public ConsoleAnnotationDescriptor(Class<? extends ConsoleNote<?>> clazz) {
+    protected ConsoleAnnotationDescriptor(Class<? extends ConsoleNote<?>> clazz) {
         super(clazz);
     }
 
-    public ConsoleAnnotationDescriptor() {
+    protected ConsoleAnnotationDescriptor() {
     }
 
     /**
diff --git a/core/src/main/java/hudson/model/Computer.java b/core/src/main/java/hudson/model/Computer.java
index efd82044bd..c6586cd354 100644
--- a/core/src/main/java/hudson/model/Computer.java
+++ b/core/src/main/java/hudson/model/Computer.java
@@ -251,7 +251,7 @@ public /*transient*/ abstract class Computer extends Actionable implements Acces
         return new ArrayList<>(terminatedBy);
     }
 
-    public Computer(Node node) {
+    protected Computer(Node node) {
         setNode(node);
     }
 
diff --git a/core/src/main/java/hudson/model/FullDuplexHttpChannel.java b/core/src/main/java/hudson/model/FullDuplexHttpChannel.java
index f7da784a93..6251bddec8 100644
--- a/core/src/main/java/hudson/model/FullDuplexHttpChannel.java
+++ b/core/src/main/java/hudson/model/FullDuplexHttpChannel.java
@@ -44,7 +44,7 @@ public abstract class FullDuplexHttpChannel extends FullDuplexHttpService {
     private Channel channel;
     private final boolean restricted;
 
-    public FullDuplexHttpChannel(UUID uuid, boolean restricted) throws IOException {
+    protected FullDuplexHttpChannel(UUID uuid, boolean restricted) throws IOException {
         super(uuid);
         this.restricted = restricted;
     }
diff --git a/core/src/main/java/hudson/model/Label.java b/core/src/main/java/hudson/model/Label.java
index 367a25f360..0e38b876f8 100644
--- a/core/src/main/java/hudson/model/Label.java
+++ b/core/src/main/java/hudson/model/Label.java
@@ -97,7 +97,7 @@ public abstract class Label extends Actionable implements Comparable<Label>, Mod
     @NonNull
     public final transient NodeProvisioner nodeProvisioner;
 
-    public Label(@NonNull String name) {
+    protected Label(@NonNull String name) {
         this.name = name;
          // passing these causes an infinite loop - getTotalExecutors(),getBusyExecutors());
         this.loadStatistics = new LoadStatistics(0,0) {
diff --git a/core/src/main/java/hudson/model/ParameterDefinition.java b/core/src/main/java/hudson/model/ParameterDefinition.java
index 740c75d977..31e98bfe49 100644
--- a/core/src/main/java/hudson/model/ParameterDefinition.java
+++ b/core/src/main/java/hudson/model/ParameterDefinition.java
@@ -102,7 +102,7 @@ public abstract class ParameterDefinition implements
 
     private String description;
 
-    public ParameterDefinition(@NonNull String name) {
+    protected ParameterDefinition(@NonNull String name) {
         if (name == null) {
             throw new IllegalArgumentException("Parameter name must be non-null");
         }
@@ -113,7 +113,7 @@ public abstract class ParameterDefinition implements
      * @deprecated Prefer {@link #ParameterDefinition(String)} with a {@link org.kohsuke.stapler.DataBoundConstructor} and allow {@link #setDescription} to be used as needed
      */
     @Deprecated
-    public ParameterDefinition(@NonNull String name, String description) {
+    protected ParameterDefinition(@NonNull String name, String description) {
         this(name);
         setDescription(description);
     }
diff --git a/core/src/main/java/hudson/model/Project.java b/core/src/main/java/hudson/model/Project.java
index b0d3c9eb6f..26232f9423 100644
--- a/core/src/main/java/hudson/model/Project.java
+++ b/core/src/main/java/hudson/model/Project.java
@@ -86,7 +86,7 @@ public abstract class Project<P extends Project<P,B>,B extends Build<P,B>>
     /**
      * Creates a new project.
      */
-    public Project(ItemGroup parent,String name) {
+    protected Project(ItemGroup parent,String name) {
         super(parent,name);
     }
 
diff --git a/core/src/main/java/hudson/model/Slave.java b/core/src/main/java/hudson/model/Slave.java
index aa0f13e47b..90b36b2c2b 100644
--- a/core/src/main/java/hudson/model/Slave.java
+++ b/core/src/main/java/hudson/model/Slave.java
@@ -164,7 +164,7 @@ public abstract class Slave extends Node implements Serializable {
      * @deprecated since 2.184
      */
     @Deprecated
-    public Slave(String name, String nodeDescription, String remoteFS, String numExecutors,
+    protected Slave(String name, String nodeDescription, String remoteFS, String numExecutors,
                  Mode mode, String labelString, ComputerLauncher launcher, RetentionStrategy retentionStrategy, List<? extends NodeProperty<?>> nodeProperties) throws FormException, IOException {
         this(name,nodeDescription,remoteFS,Util.tryParseNumber(numExecutors, 1).intValue(),mode,labelString,launcher,retentionStrategy, nodeProperties);
     }
@@ -173,12 +173,12 @@ public abstract class Slave extends Node implements Serializable {
      * @deprecated since 2009-02-20.
      */
     @Deprecated
-    public Slave(String name, String nodeDescription, String remoteFS, int numExecutors,
+    protected Slave(String name, String nodeDescription, String remoteFS, int numExecutors,
             Mode mode, String labelString, ComputerLauncher launcher, RetentionStrategy retentionStrategy) throws FormException, IOException {
     	this(name, nodeDescription, remoteFS, numExecutors, mode, labelString, launcher, retentionStrategy, new ArrayList());
     }
 
-    public Slave(@NonNull String name, String remoteFS, ComputerLauncher launcher) throws FormException, IOException {
+    protected Slave(@NonNull String name, String remoteFS, ComputerLauncher launcher) throws FormException, IOException {
         this.name = name;
         this.remoteFS = remoteFS;
         this.launcher = launcher;
@@ -189,7 +189,7 @@ public abstract class Slave extends Node implements Serializable {
      *      Use {@link #Slave(String, String, ComputerLauncher)} and set the rest through setters.
      */
     @Deprecated
-    public Slave(@NonNull String name, String nodeDescription, String remoteFS, int numExecutors,
+    protected Slave(@NonNull String name, String nodeDescription, String remoteFS, int numExecutors,
                  Mode mode, String labelString, ComputerLauncher launcher, RetentionStrategy retentionStrategy, List<? extends NodeProperty<?>> nodeProperties) throws FormException, IOException {
         this.name = name;
         this.description = nodeDescription;
diff --git a/core/src/main/java/hudson/model/labels/LabelExpression.java b/core/src/main/java/hudson/model/labels/LabelExpression.java
index 8443174fdb..00a81c2715 100644
--- a/core/src/main/java/hudson/model/labels/LabelExpression.java
+++ b/core/src/main/java/hudson/model/labels/LabelExpression.java
@@ -121,7 +121,7 @@ public abstract class LabelExpression extends Label {
     public abstract static class Binary extends LabelExpression {
         public final Label lhs,rhs;
 
-        public Binary(Label lhs, Label rhs, LabelOperatorPrecedence op) {
+        protected Binary(Label lhs, Label rhs, LabelOperatorPrecedence op) {
             super(combine(lhs, rhs, op));
             this.lhs = lhs;
             this.rhs = rhs;
diff --git a/core/src/main/java/hudson/node_monitors/AbstractDiskSpaceMonitor.java b/core/src/main/java/hudson/node_monitors/AbstractDiskSpaceMonitor.java
index c5790a436f..dce9ca3e14 100644
--- a/core/src/main/java/hudson/node_monitors/AbstractDiskSpaceMonitor.java
+++ b/core/src/main/java/hudson/node_monitors/AbstractDiskSpaceMonitor.java
@@ -18,12 +18,12 @@ public abstract class AbstractDiskSpaceMonitor extends NodeMonitor {
      */
     public final String freeSpaceThreshold;
 
-    public AbstractDiskSpaceMonitor(String threshold) throws ParseException {
+    protected AbstractDiskSpaceMonitor(String threshold) throws ParseException {
         this.freeSpaceThreshold = threshold;
         DiskSpace.parse(threshold); // make sure it parses
     }
 
-    public AbstractDiskSpaceMonitor() {
+    protected AbstractDiskSpaceMonitor() {
         this.freeSpaceThreshold = "1GB";
     }
 
diff --git a/core/src/main/java/hudson/slaves/AbstractCloudSlave.java b/core/src/main/java/hudson/slaves/AbstractCloudSlave.java
index f466f8a957..2197d8eb13 100644
--- a/core/src/main/java/hudson/slaves/AbstractCloudSlave.java
+++ b/core/src/main/java/hudson/slaves/AbstractCloudSlave.java
@@ -44,7 +44,7 @@ import jenkins.model.Jenkins;
  */
 public abstract class AbstractCloudSlave extends Slave {
 
-    public AbstractCloudSlave(@NonNull String name, String remoteFS, ComputerLauncher launcher)
+    protected AbstractCloudSlave(@NonNull String name, String remoteFS, ComputerLauncher launcher)
             throws FormException, IOException {
         super(name, remoteFS, launcher);
     }
@@ -54,7 +54,7 @@ public abstract class AbstractCloudSlave extends Slave {
      * @deprecated since 2.184
      */
     @Deprecated
-    public AbstractCloudSlave(String name, String nodeDescription, String remoteFS, String numExecutors,
+    protected AbstractCloudSlave(String name, String nodeDescription, String remoteFS, String numExecutors,
                               Mode mode, String labelString, ComputerLauncher launcher,
                               RetentionStrategy retentionStrategy, List<? extends NodeProperty<?>> nodeProperties)
             throws FormException, IOException {
@@ -66,7 +66,7 @@ public abstract class AbstractCloudSlave extends Slave {
      * @deprecated since 2.184
      */
     @Deprecated
-    public AbstractCloudSlave(String name, String nodeDescription, String remoteFS, int numExecutors,
+    protected AbstractCloudSlave(String name, String nodeDescription, String remoteFS, int numExecutors,
                               Mode mode, String labelString, ComputerLauncher launcher,
                               RetentionStrategy retentionStrategy, List<? extends NodeProperty<?>> nodeProperties)
             throws FormException, IOException {
diff --git a/core/src/main/java/hudson/slaves/ComputerLauncherFilter.java b/core/src/main/java/hudson/slaves/ComputerLauncherFilter.java
index a1c34816f6..ddc6ea0afa 100644
--- a/core/src/main/java/hudson/slaves/ComputerLauncherFilter.java
+++ b/core/src/main/java/hudson/slaves/ComputerLauncherFilter.java
@@ -41,7 +41,7 @@ import java.io.IOException;
 public abstract class ComputerLauncherFilter extends ComputerLauncher {
     protected volatile ComputerLauncher core;
 
-    public ComputerLauncherFilter(ComputerLauncher core) {
+    protected ComputerLauncherFilter(ComputerLauncher core) {
         this.core = core;
     }
 
diff --git a/core/src/main/java/hudson/tasks/CommandInterpreter.java b/core/src/main/java/hudson/tasks/CommandInterpreter.java
index fc916af2e1..f9e8c24344 100644
--- a/core/src/main/java/hudson/tasks/CommandInterpreter.java
+++ b/core/src/main/java/hudson/tasks/CommandInterpreter.java
@@ -67,7 +67,7 @@ public abstract class CommandInterpreter extends Builder implements EnvVarsFilte
     @Restricted(Beta.class)
     protected List<EnvVarsFilterLocalRule> configuredLocalRules = new ArrayList<>();
 
-    public CommandInterpreter(String command) {
+    protected CommandInterpreter(String command) {
         this.command = command;
     }
 
diff --git a/core/src/main/java/hudson/tools/AbstractCommandInstaller.java b/core/src/main/java/hudson/tools/AbstractCommandInstaller.java
index cacc982075..d3dd0d4daf 100644
--- a/core/src/main/java/hudson/tools/AbstractCommandInstaller.java
+++ b/core/src/main/java/hudson/tools/AbstractCommandInstaller.java
@@ -47,7 +47,7 @@ public abstract class AbstractCommandInstaller extends ToolInstaller {
     private final String command;
     private final String toolHome;
 
-    public AbstractCommandInstaller(String label, String command, String toolHome) {
+    protected AbstractCommandInstaller(String label, String command, String toolHome) {
         super(label);
         this.command = command;
         this.toolHome = toolHome;
diff --git a/core/src/main/java/hudson/tools/DownloadFromUrlInstaller.java b/core/src/main/java/hudson/tools/DownloadFromUrlInstaller.java
index 5661efe174..c032b92758 100644
--- a/core/src/main/java/hudson/tools/DownloadFromUrlInstaller.java
+++ b/core/src/main/java/hudson/tools/DownloadFromUrlInstaller.java
@@ -254,7 +254,7 @@ public abstract class DownloadFromUrlInstaller extends ToolInstaller {
      */
     public abstract class NodeSpecificInstallable extends Installable implements NodeSpecific<NodeSpecificInstallable> {
 
-        public NodeSpecificInstallable(Installable inst) {
+        protected NodeSpecificInstallable(Installable inst) {
             this.id = inst.id;
             this.name = inst.name;
             this.url = inst.url;
diff --git a/core/src/main/java/hudson/tools/ToolInstallation.java b/core/src/main/java/hudson/tools/ToolInstallation.java
index 49a0f0d7e2..7472c009d0 100644
--- a/core/src/main/java/hudson/tools/ToolInstallation.java
+++ b/core/src/main/java/hudson/tools/ToolInstallation.java
@@ -103,12 +103,12 @@ public abstract class ToolInstallation extends AbstractDescribableImpl<ToolInsta
      *      as of 1.302. Use {@link #ToolInstallation(String, String, List)} 
      */
     @Deprecated
-    public ToolInstallation(String name, String home) {
+    protected ToolInstallation(String name, String home) {
         this.name = name;
         this.home = home;
     }
 
-    public ToolInstallation(String name, String home, List<? extends ToolProperty<?>> properties) {
+    protected ToolInstallation(String name, String home, List<? extends ToolProperty<?>> properties) {
         this.name = name;
         this.home = home;
         if(properties!=null) {
@@ -258,7 +258,7 @@ public abstract class ToolInstallation extends AbstractDescribableImpl<ToolInsta
      * Subclasses can extend this for data migration from old field storing home directory.
      */
     protected abstract static class ToolConverter extends XStream2.PassthruConverter<ToolInstallation> {
-        public ToolConverter(XStream2 xstream) { super(xstream); }
+        protected ToolConverter(XStream2 xstream) { super(xstream); }
         @Override
         protected void callback(ToolInstallation obj, UnmarshallingContext context) {
             String s;
diff --git a/core/src/main/java/hudson/util/FormFieldValidator.java b/core/src/main/java/hudson/util/FormFieldValidator.java
index 8f5c261969..466b65b3e8 100644
--- a/core/src/main/java/hudson/util/FormFieldValidator.java
+++ b/core/src/main/java/hudson/util/FormFieldValidator.java
@@ -250,7 +250,7 @@ public abstract class FormFieldValidator {
     @Deprecated
     public abstract static class URLCheck extends FormFieldValidator {
 
-        public URLCheck(StaplerRequest request, StaplerResponse response) {
+        protected URLCheck(StaplerRequest request, StaplerResponse response) {
             // can be used to check the existence of any file in file system
             // or other HTTP URLs inside firewall, so limit this to the admin.
             super(request, response, true);
diff --git a/core/src/main/java/hudson/util/XStream2.java b/core/src/main/java/hudson/util/XStream2.java
index f72010157a..d04ceabc73 100644
--- a/core/src/main/java/hudson/util/XStream2.java
+++ b/core/src/main/java/hudson/util/XStream2.java
@@ -492,7 +492,7 @@ public class XStream2 extends XStream {
     public abstract static class PassthruConverter<T> implements Converter {
         private Converter converter;
 
-        public PassthruConverter(XStream2 xstream) {
+        protected PassthruConverter(XStream2 xstream) {
             converter = xstream.reflectionConverter;
         }
 
diff --git a/core/src/main/java/jenkins/security/RSAConfidentialKey.java b/core/src/main/java/jenkins/security/RSAConfidentialKey.java
index 8c5f64b317..35e9205350 100644
--- a/core/src/main/java/jenkins/security/RSAConfidentialKey.java
+++ b/core/src/main/java/jenkins/security/RSAConfidentialKey.java
@@ -52,11 +52,11 @@ public abstract class RSAConfidentialKey extends ConfidentialKey {
     private RSAPrivateKey priv;
     private RSAPublicKey pub;
 
-    public RSAConfidentialKey(String id) {
+    protected RSAConfidentialKey(String id) {
         super(id);
     }
 
-    public RSAConfidentialKey(Class owner, String shortName) {
+    protected RSAConfidentialKey(Class owner, String shortName) {
         this(owner.getName() + '.' + shortName);
     }
 
diff --git a/core/src/main/java/jenkins/util/InterceptingExecutorService.java b/core/src/main/java/jenkins/util/InterceptingExecutorService.java
index 6be88667c7..beb1e363bf 100644
--- a/core/src/main/java/jenkins/util/InterceptingExecutorService.java
+++ b/core/src/main/java/jenkins/util/InterceptingExecutorService.java
@@ -19,7 +19,7 @@ import java.util.concurrent.TimeoutException;
 public abstract class InterceptingExecutorService implements ExecutorService {
     private final ExecutorService base;
 
-    public InterceptingExecutorService(ExecutorService base) {
+    protected InterceptingExecutorService(ExecutorService base) {
         this.base = base;
     }
 
diff --git a/core/src/main/java/jenkins/util/MarkFindingOutputStream.java b/core/src/main/java/jenkins/util/MarkFindingOutputStream.java
index 09d42c0639..1c5d52e85c 100644
--- a/core/src/main/java/jenkins/util/MarkFindingOutputStream.java
+++ b/core/src/main/java/jenkins/util/MarkFindingOutputStream.java
@@ -15,7 +15,7 @@ import java.nio.charset.StandardCharsets;
 public abstract class MarkFindingOutputStream extends OutputStream {
     private final OutputStream base;
 
-    public MarkFindingOutputStream(OutputStream base) {
+    protected MarkFindingOutputStream(OutputStream base) {
         this.base = base;
     }
 
diff --git a/core/src/main/java/jenkins/util/groovy/AbstractGroovyViewModule.java b/core/src/main/java/jenkins/util/groovy/AbstractGroovyViewModule.java
index 97dc9b22e0..ba4391ebee 100644
--- a/core/src/main/java/jenkins/util/groovy/AbstractGroovyViewModule.java
+++ b/core/src/main/java/jenkins/util/groovy/AbstractGroovyViewModule.java
@@ -25,7 +25,7 @@ public abstract class AbstractGroovyViewModule extends GroovyObjectSupport {
     public JenkinsTagLib t;
     public Namespace st;
 
-    public AbstractGroovyViewModule(JellyBuilder b) {
+    protected AbstractGroovyViewModule(JellyBuilder b) {
         builder = b;
         f = builder.namespace(FormTagLib.class);
         l = builder.namespace(LayoutTagLib.class);
diff --git a/core/src/main/java/org/acegisecurity/AcegiSecurityException.java b/core/src/main/java/org/acegisecurity/AcegiSecurityException.java
index bfc529de38..d4e780fe57 100644
--- a/core/src/main/java/org/acegisecurity/AcegiSecurityException.java
+++ b/core/src/main/java/org/acegisecurity/AcegiSecurityException.java
@@ -32,11 +32,11 @@ import org.springframework.core.NestedRuntimeException;
 @Deprecated
 public abstract class AcegiSecurityException extends NestedRuntimeException {
 
-    public AcegiSecurityException(String msg) {
+    protected AcegiSecurityException(String msg) {
         super(msg);
     }
     
-    public AcegiSecurityException(String msg, Throwable cause) {
+    protected AcegiSecurityException(String msg, Throwable cause) {
         super(msg, cause);
     }
 
diff --git a/core/src/main/java/org/acegisecurity/AuthenticationException.java b/core/src/main/java/org/acegisecurity/AuthenticationException.java
index ff3f9bc9a5..22a3fc3980 100644
--- a/core/src/main/java/org/acegisecurity/AuthenticationException.java
+++ b/core/src/main/java/org/acegisecurity/AuthenticationException.java
@@ -38,16 +38,16 @@ public abstract class AuthenticationException extends AcegiSecurityException {
     private Authentication authentication;
     private Object extraInformation;
 
-    public AuthenticationException(String msg) {
+    protected AuthenticationException(String msg) {
         super(msg);
     }
 
-    public AuthenticationException(String msg, Object extraInformation) {
+    protected AuthenticationException(String msg, Object extraInformation) {
         super(msg);
         this.extraInformation = extraInformation;
     }
 
-    public AuthenticationException(String msg, Throwable t) {
+    protected AuthenticationException(String msg, Throwable t) {
         super(msg, t);
     }
 
diff --git a/core/src/main/java/org/acegisecurity/providers/AbstractAuthenticationToken.java b/core/src/main/java/org/acegisecurity/providers/AbstractAuthenticationToken.java
index 266e581e40..63cbeb0aec 100644
--- a/core/src/main/java/org/acegisecurity/providers/AbstractAuthenticationToken.java
+++ b/core/src/main/java/org/acegisecurity/providers/AbstractAuthenticationToken.java
@@ -40,11 +40,11 @@ public abstract class AbstractAuthenticationToken implements Authentication {
     private Object details;
     private boolean authenticated;
 
-    public AbstractAuthenticationToken() {
+    protected AbstractAuthenticationToken() {
         this.authorities = new GrantedAuthority[0];
     }
 
-    public AbstractAuthenticationToken(GrantedAuthority[] authorities) {
+    protected AbstractAuthenticationToken(GrantedAuthority[] authorities) {
         this.authorities = authorities;
     }