import java.lang.ref.WeakReference;
import java.util.ConcurrentModificationException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import javax.annotation.CheckForNull;

/**
 * A builder of {@link ConcurrentMap} instances that can have keys or values automatically wrapped
 * in {@linkplain WeakReference weak} references.
 *
 * <p>Usage example:

    AtomicReference<Object> sepStopwatchA =
        new AtomicReference<Object>(sepStopwatchC.getMethod("createUnstarted").invoke(null));
    AtomicReference<WeakReference<?>> sepStopwatchRef =
        new AtomicReference<WeakReference<?>>(
            (WeakReference<?>) sepFwrCons.newInstance(sepStopwatchA.get(), sepFrqA.get()));
    assertNotNull(sepStopwatchA.get());
    // Clear all references to the Stopwatch and wait for it to be gc'd.

 * leaks, by ensuring that objects are no longer strongly referenced:
 *
 * <pre>{@code
 * // Helper function keeps victim stack-unreachable.
 * private WeakReference<Foo> fooWeakRef() {
 *   Foo x = ....;
 *   WeakReference<Foo> weakRef = new WeakReference<>(x);
 *   // ... use x ...
 *   x = null;  // Hint to the JIT that x is stack-unreachable
 *   return weakRef;
 * }
 * public void testFooLeak() {

import java.lang.ref.WeakReference;
import java.util.ConcurrentModificationException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import javax.annotation.CheckForNull;

/**
 * A builder of {@link ConcurrentMap} instances that can have keys or values automatically wrapped
 * in {@linkplain WeakReference weak} references.
 *
 * <p>Usage example:

 * leaks, by ensuring that objects are no longer strongly referenced:
 *
 * <pre>{@code
 * // Helper function keeps victim stack-unreachable.
 * private WeakReference<Foo> fooWeakRef() {
 *   Foo x = ....;
 *   WeakReference<Foo> weakRef = new WeakReference<>(x);
 *   // ... use x ...
 *   x = null;  // Hint to the JIT that x is stack-unreachable
 *   return weakRef;
 * }
 * public void testFooLeak() {

                mapping.classLoaders.add(new WeakReference<>(candidate));
            }
            classLoaders.put(uuid, mapping);
            return mapping.details;
        } finally {
            lock.unlock();
        }
    }

    private static class LocalClassLoaderMapping {
        private final Set<WeakReference<ClassLoader>> classLoaders = new LinkedHashSet<>();

       * UnsignedBytesBenchmark. TODO(cpovirk): benchmark this
       */
      /*
       * A CopyOnWriteArraySet<WeakReference> is faster than a newSetFromMap of a MapMaker map with
       * weakKeys() and concurrencyLevel(1), even up to at least 12 cached exception types.
       */
      private static final Set<WeakReference<Class<? extends Exception>>> validClasses =
          new CopyOnWriteArraySet<>();

      @Override

       * UnsignedBytesBenchmark. TODO(cpovirk): benchmark this
       */
      /*
       * A CopyOnWriteArraySet<WeakReference> is faster than a newSetFromMap of a MapMaker map with
       * weakKeys() and concurrencyLevel(1), even up to at least 12 cached exception types.
       */
      private static final Set<WeakReference<Class<? extends Exception>>> validClasses =
          new CopyOnWriteArraySet<>();

      @Override

import com.google.common.util.concurrent.FuturesGetCheckedInputs.TwoArgConstructorException;
import com.google.common.util.concurrent.FuturesGetCheckedInputs.TwoArgConstructorRuntimeException;
import java.lang.ref.WeakReference;
import java.net.URLClassLoader;
import java.util.concurrent.CancellationException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import com.google.common.util.concurrent.FuturesGetCheckedInputs.TwoArgConstructorException;
import com.google.common.util.concurrent.FuturesGetCheckedInputs.TwoArgConstructorRuntimeException;
import java.lang.ref.WeakReference;
import java.net.URLClassLoader;
import java.util.concurrent.CancellationException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;