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/*
* Copyright (c) 2019, 2022, 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.
*
* 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.
*/
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
/**
* Helper class for creating Thread buidlers.
*
* Tests using this class need to open java.base/java.lang.
*/
class ThreadBuilders {
private ThreadBuilders() { }
private static final Constructor<?> VTBUILDER_CTOR;
static {
try {
Class<?> clazz = Class.forName("java.lang.ThreadBuilders$VirtualThreadBuilder");
Constructor<?> ctor = clazz.getDeclaredConstructor(Executor.class);
ctor.setAccessible(true);
VTBUILDER_CTOR = ctor;
} catch (Exception e) {
throw new InternalError(e);
}
}
/**
* Returns a builder to create virtual threads that use the given scheduler.
* @throws UnsupportedOperationException if custom schedulers are not supported
*/
static Thread.Builder.OfVirtual virtualThreadBuilder(Executor scheduler) {
try {
return (Thread.Builder.OfVirtual) VTBUILDER_CTOR.newInstance(scheduler);
} catch (InvocationTargetException e) {
Throwable cause = e.getCause();
if (cause instanceof RuntimeException re) {
throw re;
}
throw new RuntimeException(e);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
/**
* Return true if custom schedulers are supported.
*/
static boolean supportsCustomScheduler() {
try (var pool = Executors.newCachedThreadPool()) {
try {
virtualThreadBuilder(pool);
return true;
} catch (UnsupportedOperationException e) {
return false;
}
}
}
}
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