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/*
 * Copyright (C) 2009 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.Supplier;
import java.util.concurrent.Callable;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Static utility methods pertaining to the {@link Callable} interface.
 *
 * @author Isaac Shum
 * @since 1.0
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public final class Callables {
  private Callables() {}

  /** Creates a {@code Callable} which immediately returns a preset value each time it is called. */
  public static  Callable returning(@ParametricNullness T value) {
    return () -> value;
  }

  /**
   * Creates an {@link AsyncCallable} from a {@link Callable}.
   *
   * 

The {@link AsyncCallable} returns the {@link ListenableFuture} resulting from {@link * ListeningExecutorService#submit(Callable)}. * * @since 20.0 */ @J2ktIncompatible @GwtIncompatible public static AsyncCallable asAsyncCallable( Callable callable, ListeningExecutorService listeningExecutorService) { checkNotNull(callable); checkNotNull(listeningExecutorService); return () -> listeningExecutorService.submit(callable); } /** * Wraps the given callable such that for the duration of {@link Callable#call} the thread that is * running will have the given name. * * @param callable The callable to wrap * @param nameSupplier The supplier of thread names, {@link Supplier#get get} will be called once * for each invocation of the wrapped callable. */ @J2ktIncompatible @GwtIncompatible // threads static Callable threadRenaming( Callable callable, Supplier nameSupplier) { checkNotNull(nameSupplier); checkNotNull(callable); return () -> { Thread currentThread = Thread.currentThread(); String oldName = currentThread.getName(); boolean restoreName = trySetName(nameSupplier.get(), currentThread); try { return callable.call(); } finally { if (restoreName) { boolean unused = trySetName(oldName, currentThread); } } }; } /** * Wraps the given runnable such that for the duration of {@link Runnable#run} the thread that is * running with have the given name. * * @param task The Runnable to wrap * @param nameSupplier The supplier of thread names, {@link Supplier#get get} will be called once * for each invocation of the wrapped callable. */ @J2ktIncompatible @GwtIncompatible // threads static Runnable threadRenaming(Runnable task, Supplier nameSupplier) { checkNotNull(nameSupplier); checkNotNull(task); return () -> { Thread currentThread = Thread.currentThread(); String oldName = currentThread.getName(); boolean restoreName = trySetName(nameSupplier.get(), currentThread); try { task.run(); } finally { if (restoreName) { boolean unused = trySetName(oldName, currentThread); } } }; } /** Tries to set name of the given {@link Thread}, returns true if successful. */ @J2ktIncompatible @GwtIncompatible // threads private static boolean trySetName(String threadName, Thread currentThread) { /* * setName should usually succeed, but the security manager can prohibit it. Is there a way to * see if we have the modifyThread permission without catching an exception? */ try { currentThread.setName(threadName); return true; } catch (SecurityException e) { return false; } } }





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