8264001: JFR: Modernize implementation

Reviewed-by: mgronlun

Author: egahlin

src/jdk.jfr/share/classes/jdk/jfr/AnnotationElement.java

@@ -100,7 +100,7 @@ public final class AnnotationElement {
             }
             checkType(Utils.unboxType(valueType));
         }
-        this.annotationValues = Utils.smallUnmodifiable(objects);
+        this.annotationValues = List.copyOf(objects);
         this.inBootClassLoader = boot;
     }
 
@@ -203,7 +203,7 @@ public AnnotationElement(Class<? extends Annotation> annotationType, Map<String,
             }
             v.add(object);
         }
-        this.annotationValues = Utils.smallUnmodifiable(v);
+        this.annotationValues = List.copyOf(v);
         this.inBootClassLoader = annotationType.getClassLoader() == null;
     }
 

src/jdk.jfr/share/classes/jdk/jfr/Configuration.java

@@ -30,8 +30,6 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.text.ParseException;
-import java.util.ArrayList;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -190,8 +188,8 @@ public static Configuration getConfiguration(String name) throws IOException, Pa
      */
     public static List<Configuration> getConfigurations() {
         if (JVMSupport.isNotAvailable()) {
-            return new ArrayList<>();
+            return List.of();
         }
-        return Collections.unmodifiableList(JFC.getConfigurations());
+        return List.copyOf(JFC.getConfigurations());
     }
 }

src/jdk.jfr/share/classes/jdk/jfr/Event.java

@@ -97,6 +97,7 @@ protected Event() {
     /**
      * Starts the timing of this event.
      */
+    @Override
     final public void begin() {
     }
 
@@ -105,6 +106,7 @@ final public void begin() {
      *
      * The {@code end} method must be invoked after the {@code begin} method.
      */
+    @Override
     final public void end() {
     }
 
@@ -116,6 +118,7 @@ final public void end() {
      * not end with an explicit invocation of the {@code end} method, then the event
      * ends when the {@code commit} method is invoked.
      */
+    @Override
     final public void commit() {
     }
 
@@ -126,6 +129,7 @@ final public void commit() {
      *
      * @return {@code true} if event is enabled, {@code false} otherwise
      */
+    @Override
     final public boolean isEnabled() {
         return false;
     }
@@ -139,6 +143,7 @@ final public boolean isEnabled() {
      * @return {@code true} if the event can be written to the Flight Recorder
      *         system, {@code false} otherwise
      */
+    @Override
     final public boolean shouldCommit() {
         return false;
     }
@@ -164,6 +169,7 @@ final public boolean shouldCommit() {
      * @see EventType#getFields()
      * @see EventFactory
      */
+    @Override
     final public void set(int index, Object value) {
     }
 }

src/jdk.jfr/share/classes/jdk/jfr/EventType.java

@@ -26,7 +26,6 @@
 package jdk.jfr;
 
 import java.lang.annotation.Annotation;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -45,8 +44,8 @@
  * @since 9
  */
 public final class EventType {
+    private static final List<String> UNCATEGORIZED = List.of("Uncategorized");
     private final PlatformEventType platformEventType;
-    private final List<String> UNCATEGORIZED = Collections.singletonList("Uncategorized");
     private Map<String, ValueDescriptor> cache; // create lazy to avoid memory overhead
     // helper constructor
     EventType(PlatformEventType platformEventType) {
@@ -79,11 +78,11 @@ public ValueDescriptor getField(String name) {
         Objects.requireNonNull(name);
         if (cache == null) {
             List<ValueDescriptor> fields = getFields();
-            Map<String, ValueDescriptor> newCache = new LinkedHashMap<String, ValueDescriptor>(fields.size());
+            Map<String, ValueDescriptor> newCache = new LinkedHashMap<>(fields.size());
             for (ValueDescriptor v :fields) {
                 newCache.put(v.getName(), v);
             }
-            cache = newCache;
+            cache = Map.copyOf(newCache);
         }
         ValueDescriptor result = cache.get(name);
         if (result == null) {
@@ -230,7 +229,7 @@ public List<String> getCategoryNames() {
         if (c == null) {
             return UNCATEGORIZED;
         }
-        return Collections.unmodifiableList(Arrays.asList(c.value()));
+        return List.of(c.value());
     }
 
     // package private

src/jdk.jfr/share/classes/jdk/jfr/FlightRecorder.java

@@ -38,7 +38,6 @@
 
 import jdk.jfr.internal.JVM;
 import jdk.jfr.internal.JVMSupport;
-import jdk.jfr.internal.LogLevel;
 import jdk.jfr.internal.Logger;
 import jdk.jfr.internal.MetadataRepository;
 import jdk.jfr.internal.Options;

src/jdk.jfr/share/classes/jdk/jfr/FlightRecorderPermission.java

@@ -26,7 +26,6 @@
 package jdk.jfr;
 
 import java.security.AccessControlContext;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -109,17 +108,17 @@ private final static class InternalAccess extends PrivateAccess {
 
         @Override
         public Type getType(Object o) {
-            if (o instanceof AnnotationElement) {
-                return ((AnnotationElement) o).getType();
+            if (o instanceof AnnotationElement ae) {
+                return ae.getType();
             }
-            if (o instanceof EventType) {
-                return ((EventType) o).getType();
+            if (o instanceof EventType et) {
+                return et.getType();
             }
-            if (o instanceof ValueDescriptor) {
-                return ((ValueDescriptor) o).getType();
+            if (o instanceof ValueDescriptor vd) {
+                return vd.getType();
             }
-            if (o instanceof SettingDescriptor) {
-                return ((SettingDescriptor) o).getType();
+            if (o instanceof SettingDescriptor sd) {
+                return sd.getType();
             }
             throw new Error("Unknown type " + o.getClass());
         }
@@ -176,7 +175,7 @@ public String getFieldName(ValueDescriptor v) {
 
         @Override
         public ValueDescriptor newValueDescriptor(Class<?> type, String name) {
-            return new ValueDescriptor(type, name, Collections.emptyList(), true);
+            return new ValueDescriptor(type, name, List.of(), true);
         }
 
         @Override

src/jdk.jfr/share/classes/jdk/jfr/Recording.java

@@ -135,7 +135,7 @@ public Recording(Map<String, String> settings) {
      *         FlightRecorderPermission "accessFlightRecorder" is not set.
      */
     public Recording() {
-        this(new HashMap<String, String>());
+        this(Map.of());
      }
 
     /**

src/jdk.jfr/share/classes/jdk/jfr/SettingDescriptor.java

@@ -26,7 +26,6 @@
 package jdk.jfr;
 
 import java.lang.annotation.Annotation;
-import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
 
@@ -196,7 +195,7 @@ public <A extends Annotation> A getAnnotation(Class<A> annotationType) {
      * @return a list of annotations, not {@code null}
      */
     public List<AnnotationElement> getAnnotationElements() {
-        return Collections.unmodifiableList(annotationConstruct.getUnmodifiableAnnotationElements());
+        return annotationConstruct.getUnmodifiableAnnotationElements();
     }
 
     /**

src/jdk.jfr/share/classes/jdk/jfr/ValueDescriptor.java

@@ -26,7 +26,6 @@
 package jdk.jfr;
 
 import java.lang.annotation.Annotation;
-import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
@@ -131,7 +130,7 @@ public ValueDescriptor(Class<?> type, String name) {
      *         doesn't have {@code FlightRecorderPermission("registerEvent")}
      */
     public ValueDescriptor(Class<?> type, String name, List<AnnotationElement> annotations) {
-        this(type, name, new ArrayList<>(annotations), false);
+        this(type, name, List.copyOf(annotations), false);
     }
 
 
@@ -289,7 +288,7 @@ public List<AnnotationElement> getAnnotationElements() {
      */
     public List<ValueDescriptor> getFields() {
         if (type.isSimpleType()) {
-            return Collections.emptyList();
+            return List.of();
         }
         return type.getFields();
     }

src/jdk.jfr/share/classes/jdk/jfr/consumer/EventStream.java

@@ -263,6 +263,7 @@ default void onMetadata(Consumer<MetadataEvent> action) {
      * <p>
      * Closing a previously closed stream has no effect.
      */
+    @Override
     void close();
 
     /**