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	/*
	* Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package jdk.jfr;

	import java.lang.annotation.Annotation;
	import java.util.Arrays;
	import java.util.Collections;
	import java.util.LinkedHashMap;
	import java.util.List;
	import java.util.Map;
	import java.util.Objects;

	import jdk.jfr.internal.JVMSupport;
	import jdk.jfr.internal.MetadataRepository;
	import jdk.jfr.internal.PlatformEventType;
	import jdk.jfr.internal.Type;
	import jdk.jfr.internal.Utils;

	/**
	* Describes an event, its fields, settings and annotations.
	*
	* @since 8
	*/
	public final class EventType {
	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) {
	this.platformEventType = platformEventType;
	}

	/**
	* Returns an immutable list of descriptors that describe the event fields of
	* this event type.
	*
	* @return the list of field descriptors, not {@code null}
	*/
	public List<ValueDescriptor> getFields() {
	return platformEventType.getFields();
	}

	/**
	* Returns the field with the specified name, or {@code null} if it doesn't
	* exist.
	*
	* @return a value descriptor that describes the field, or <code>null</code> if
	* the field with the specified name doesn't exist
	*
	* @return a value descriptor, or <code>null</code> if it doesn't exist
	*/
	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());
	for (ValueDescriptor v :fields) {
	newCache.put(v.getName(), v);
	}
	cache = newCache;
	}
	return cache.get(name);
	}

	/**
	* Returns an identifier for the event (for example,
	* {@code "jdk.CPULoad"}).
	* <p>
	* The identifier is the fully qualified name of the event class, if not set using
	* the {@link Name} annotation.
	*
	* @return the name, not {@code null}
	*
	* @see Name
	*/
	public String getName() {
	return platformEventType.getName();
	}

	/**
	* Returns a human-readable name (for example, {@code "CPU Load"}).
	* <p>
	* The label of an event class can be set with {@link Label}.
	*
	* @return the label, or {@code null} if a label is not set
	*
	* @see Label
	*/
	public String getLabel() {
	return platformEventType.getLabel();
	}

	/**
	* Returns a unique ID for this event type in the Java Virtual Machine (JVM).
	*
	* @return the ID that is used in the JVM
	*/
	public long getId() {
	return platformEventType.getId();
	}

	/**
	* Returns an immutable list of annotation elements for this event type.
	*
	* @return an immutable list of annotations or an empty list if no
	* annotations exists, not {@code null}
	*/
	public List<AnnotationElement> getAnnotationElements() {
	return platformEventType.getAnnotationElements();
	}

	/**
	* Returns {@code true} if the event is enabled and at least one recording is
	* running, {@code false} otherwise.
	* <p>
	* By default, the event is enabled. The event can be enabled or disabled by
	* setting the enabled setting to {@code true} or {@code false}, programmatically or by using a
	* configuration file. The event can also be disabled by annotating event with
	* the {@code @Enabled(false)} annotation.
	*
	* @return true if event is enabled, false otherwise
	*
	* @see Enabled
	* @see Recording#enable(Class)
	*/
	public boolean isEnabled() {
	return platformEventType.isEnabled();
	}

	/**
	* Returns a short sentence that describes the event class.
	* <p>
	* The description of an event class can be set with {@link Description}.
	*
	* @return the description, or {@code null} if no description exists
	*
	* @see Description
	*/
	public String getDescription() {
	return platformEventType.getDescription();
	}

	/**
	* Returns the first annotation for the specified type if an annotation
	* element with the same name is directly present, otherwise {@code null}.
	*
	* @param <A> the type of the annotation to query for and return if present
	* @param annotationClass the {@code Class} object that corresponds to the
	* annotation type, not {@code null}
	* @return this element's annotation for the specified annotation type if
	* directly present, else {@code null}
	*/
	public <A extends Annotation> A getAnnotation(Class<A> annotationClass) {
	Objects.requireNonNull(annotationClass);
	return platformEventType.getAnnotation(annotationClass);
	}

	/**
	* Returns the event type for an event class, or {@code null} if it doesn't
	* exist.
	*
	* @param eventClass the event class, not {@code null}
	* @return the event class, or null if class doesn't exist
	*
	* @throws IllegalArgumentException if {@code eventClass} is an abstract class
	*
	* @throws IllegalStateException if the class is annotated with
	* {@code Registered(false)}, but not manually registered
	*/
	public static EventType getEventType(Class<? extends Event> eventClass) {
	Objects.requireNonNull(eventClass);
	Utils.ensureValidEventSubclass(eventClass);
	JVMSupport.ensureWithInternalError();
	return MetadataRepository.getInstance().getEventType(eventClass);
	}

	/**
	* Returns an immutable list of the setting descriptors that describe the available
	* event settings for this event type.
	*
	* @return the list of setting descriptors for this event type, not
	* {@code null}
	*/
	public List<SettingDescriptor> getSettingDescriptors() {
	return Collections.unmodifiableList(platformEventType.getSettings());
	}

	/**
	* Returns the list of human-readable names that makes up the categories for
	* this event type (for example, {@code "Java Application"}, {@code "Statistics"}).
	*
	* @return an immutable list of category names, or a list with the name
	* {@code "Uncategorized"} if no category is set
	*
	* @see Category
	*/
	public List<String> getCategoryNames() {
	Category c = platformEventType.getAnnotation(Category.class);
	if (c == null) {
	return UNCATEGORIZED;
	}
	return Collections.unmodifiableList(Arrays.asList(c.value()));
	}

	// package private
	Type getType() {
	return platformEventType;
	}

	// package private
	PlatformEventType getPlatformEventType() {
	return platformEventType;
	}
	}

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