Migrate code base to Java 21

cli/src/main/java/hudson/cli/CLI.java

@@ -138,40 +138,45 @@ public static int _main(String[] _args) throws Exception {
 
         while (!args.isEmpty()) {
             String head = args.get(0);
-            if (head.equals("-version")) {
-                System.out.println("Version: " + computeVersion());
-                return 0;
-            }
-            if (head.equals("-http")) {
-                if (mode != null) {
-                    printUsage("-http clashes with previously defined mode " + mode);
-                    return -1;
+            switch (head) {
+                case "-version" -> {
+                    System.out.println("Version: " + computeVersion());
+                    return 0;
                 }
-                mode = Mode.HTTP;
-                args = args.subList(1, args.size());
-                continue;
-            }
-            if (head.equals("-ssh")) {
-                if (mode != null) {
-                    printUsage("-ssh clashes with previously defined mode " + mode);
-                    return -1;
+                case "-http" -> {
+                    if (mode != null) {
+                        printUsage("-http clashes with previously defined mode " + mode);
+                        return -1;
+                    }
+                    mode = Mode.HTTP;
+                    args = args.subList(1, args.size());
+                    continue;
                 }
-                mode = Mode.SSH;
-                args = args.subList(1, args.size());
-                continue;
-            }
-            if (head.equals("-webSocket")) {
-                if (mode != null) {
-                    printUsage("-webSocket clashes with previously defined mode " + mode);
+                case "-ssh" -> {
+                    if (mode != null) {
+                        printUsage("-ssh clashes with previously defined mode " + mode);
+                        return -1;
+                    }
+                    mode = Mode.SSH;
+                    args = args.subList(1, args.size());
+                    continue;
+                }
+                case "-webSocket" -> {
+                    if (mode != null) {
+                        printUsage("-webSocket clashes with previously defined mode " + mode);
+                        return -1;
+                    }
+                    mode = Mode.WEB_SOCKET;
+                    args = args.subList(1, args.size());
+                    continue;
+                }
+                case "-remoting" -> {
+                    printUsage("-remoting mode is no longer supported");
                     return -1;
                 }
-                mode = Mode.WEB_SOCKET;
-                args = args.subList(1, args.size());
-                continue;
-            }
-            if (head.equals("-remoting")) {
-                printUsage("-remoting mode is no longer supported");
-                return -1;
+                default -> {
+                    // continue
+                }
             }
             if (head.equals("-s") && args.size() >= 2) {
                 url = args.get(1);

cli/src/main/java/hudson/cli/PlainCLIProtocol.java

@@ -262,28 +262,33 @@ abstract static class ServerSide extends EitherSide {
         @Override
         protected final boolean handle(Op op, DataInputStream dis) throws IOException {
             assert op.clientSide;
-            switch (op) {
-            case ARG:
-                onArg(dis.readUTF());
-                return true;
-            case LOCALE:
-                onLocale(dis.readUTF());
-                return true;
-            case ENCODING:
-                onEncoding(dis.readUTF());
-                return true;
-            case START:
-                onStart();
-                return true;
-            case STDIN:
-                onStdin(dis.readAllBytes());
-                return true;
-            case END_STDIN:
-                onEndStdin();
-                return true;
-            default:
-                return false;
-            }
+            return switch (op) {
+                case ARG -> {
+                    onArg(dis.readUTF());
+                    yield true;
+                }
+                case LOCALE -> {
+                    onLocale(dis.readUTF());
+                    yield true;
+                }
+                case ENCODING -> {
+                    onEncoding(dis.readUTF());
+                    yield true;
+                }
+                case START -> {
+                    onStart();
+                    yield true;
+                }
+                case STDIN -> {
+                    onStdin(dis.readAllBytes());
+                    yield true;
+                }
+                case END_STDIN -> {
+                    onEndStdin();
+                    yield true;
+                }
+                default -> false;
+            };
         }
 
         protected abstract void onArg(String text);
@@ -321,19 +326,21 @@ abstract static class ClientSide extends EitherSide {
         @Override
         protected boolean handle(Op op, DataInputStream dis) throws IOException {
             assert !op.clientSide;
-            switch (op) {
-            case EXIT:
-                onExit(dis.readInt());
-                return true;
-            case STDOUT:
-                onStdout(dis.readAllBytes());
-                return true;
-            case STDERR:
-                onStderr(dis.readAllBytes());
-                return true;
-            default:
-                return false;
-            }
+            return switch (op) {
+                case EXIT -> {
+                    onExit(dis.readInt());
+                    yield true;
+                }
+                case STDOUT -> {
+                    onStdout(dis.readAllBytes());
+                    yield true;
+                }
+                case STDERR -> {
+                    onStderr(dis.readAllBytes());
+                    yield true;
+                }
+                default -> false;
+            };
         }
 
         protected abstract void onExit(int code);

cli/src/main/java/hudson/cli/SSHCLI.java

@@ -29,12 +29,10 @@
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import hudson.util.QuotedStringTokenizer;
 import java.io.IOException;
-import java.net.SocketAddress;
 import java.net.SocketTimeoutException;
 import java.net.URL;
 import java.net.URLConnection;
 import java.security.KeyPair;
-import java.security.PublicKey;
 import java.util.List;
 import java.util.Set;
 import java.util.logging.Level;
@@ -45,7 +43,6 @@
 import org.apache.sshd.client.future.ConnectFuture;
 import org.apache.sshd.client.keyverifier.DefaultKnownHostsServerKeyVerifier;
 import org.apache.sshd.client.keyverifier.KnownHostsServerKeyVerifier;
-import org.apache.sshd.client.keyverifier.ServerKeyVerifier;
 import org.apache.sshd.client.session.ClientSession;
 import org.apache.sshd.common.future.WaitableFuture;
 import org.apache.sshd.common.util.io.input.NoCloseInputStream;
@@ -86,12 +83,9 @@ static int sshConnection(String jenkinsUrl, String user, List<String> args, Priv
 
         try (SshClient client = SshClient.setUpDefaultClient()) {
 
-            KnownHostsServerKeyVerifier verifier = new DefaultKnownHostsServerKeyVerifier(new ServerKeyVerifier() {
-                @Override
-                public boolean verifyServerKey(ClientSession clientSession, SocketAddress remoteAddress, PublicKey serverKey) {
-                    CLI.LOGGER.log(Level.WARNING, "Unknown host key for {0}", remoteAddress.toString());
-                    return !strictHostKey;
-                }
+            KnownHostsServerKeyVerifier verifier = new DefaultKnownHostsServerKeyVerifier((clientSession, remoteAddress, serverKey) -> {
+                CLI.LOGGER.log(Level.WARNING, "Unknown host key for {0}", remoteAddress.toString());
+                return !strictHostKey;
             }, true);
 
             client.setServerKeyVerifier(verifier);

core/src/main/java/hudson/EnvVars.java

@@ -282,7 +282,7 @@ private void cutCycle(List<String> cycle) {
             }
 
             // if not, cut the reference to the first one.
-            cutCycleAt(cycle.get(0), cycle);
+            cutCycleAt(cycle.getFirst(), cycle);
         }
 
         /**

core/src/main/java/hudson/ExtensionFinder.java

@@ -628,7 +628,7 @@
                             .flatMap(Collection::stream)
                             .filter(m -> m.getAnnotation(PostConstruct.class) != null || m.getAnnotation(javax.annotation.PostConstruct.class) != null)
                             .findFirst()
-                            .ifPresent(method -> methods.add(0, method));
+                            .ifPresent(methods::addFirst);
                     c = c.getSuperclass();
                 }
 
@@ -788,16 +788,12 @@
 
     private static Class<?> getClassFromIndex(IndexItem<Extension, Object> item) throws InstantiationException {
         AnnotatedElement e = item.element();
-        Class<?> extType;
-        if (e instanceof Class) {
-            extType = (Class) e;
-        } else if (e instanceof Field) {
-            extType = ((Field) e).getType();
-        } else if (e instanceof Method) {
-            extType = ((Method) e).getReturnType();
-        } else {
-            throw new AssertionError();
-        }
+        Class<?> extType = switch (e) {
+            case Class aClass -> aClass;
+            case Field field -> field.getType();
+            case Method method -> method.getReturnType();
+            case null, default -> throw new AssertionError();
+        };
         return extType;
     }
 

core/src/main/java/hudson/ExtensionList.java

@@ -457,7 +457,7 @@ public static <T> ExtensionList<T> create(Jenkins jenkins, Class<T> type) {
         } else if (all.size() != 1) {
             throw new IllegalStateException("Expected 1 instance of " + type.getName() + " but got " + all.size());
         }
-        return all.get(0);
+        return all.getFirst();
     }
 
     /**
@@ -474,7 +474,7 @@ public static <T> ExtensionList<T> create(Jenkins jenkins, Class<T> type) {
     public static @NonNull <U> U lookupFirst(Class<U> type) {
         var all = lookup(type);
         if (!all.isEmpty()) {
-            return all.get(0);
+            return all.getFirst();
         } else {
             if (Main.isUnitTest) {
                 throw new IllegalStateException("Found no instances of " + type.getName() +

core/src/main/java/hudson/FilePath.java

@@ -350,15 +350,15 @@
                 if (i == 0) {
                     // If absolute path, just remove: /../something
                     // If relative path, not collapsible so leave as-is
-                    tokens.remove(0);
-                    if (!tokens.isEmpty()) token += tokens.remove(0);
+                    tokens.removeFirst();
+                    if (!tokens.isEmpty()) token += tokens.removeFirst();
                     if (!isAbsolute) buf.append(token);
                 } else {
                     // Normalize: remove something/.. plus separator before/after
                     i -= 2;
                     for (int j = 0; j < 3; j++) tokens.remove(i);
                     if (i > 0) tokens.remove(i - 1);
-                    else if (!tokens.isEmpty()) tokens.remove(0);
+                    else if (!tokens.isEmpty()) tokens.removeFirst();
                 }
             } else
                 i += 2;

core/src/main/java/hudson/Functions.java

@@ -142,6 +142,7 @@
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
 import java.util.SortedMap;
@@ -1278,11 +1279,8 @@ public static boolean hasAnyPermission(Object object, Permission[] permissions)
             return hasAnyPermission((AccessControlled) object, permissions);
         else {
             AccessControlled ac = Stapler.getCurrentRequest2().findAncestorObject(AccessControlled.class);
-            if (ac != null) {
-                return hasAnyPermission(ac, permissions);
-            }
+            return hasAnyPermission(Objects.requireNonNullElseGet(ac, Jenkins::get), permissions);
 
-            return hasAnyPermission(Jenkins.get(), permissions);
         }
     }
 

core/src/main/java/hudson/MarkupText.java

@@ -266,7 +266,7 @@ public void addMarkup(int startPos, int endPos, String startTag, String endTag)
         // <b><i>abc</i></b>, not <b><i>abc</b></i>. Also, we'd like <b>abc</b><i>def</i>,
         // not <b>abc<i></b>def</i>. Do this by inserting them to different places.
         tags.add(new Tag(startPos, startTag));
-        tags.add(0, new Tag(endPos, endTag));
+        tags.addFirst(new Tag(endPos, endTag));
     }
 
     public void addMarkup(int pos, String tag) {