enabling the HTTP/2 use by the HTTP client broke programs
connecting to servers with buggy HTTP/2 implementations.
These kinds of changes are unavoidable and
[permitted by the Go 1 compatibility rules](/doc/go1compat).
Even so, Go provides a mechanism called GODEBUG to
reduce the impact such changes have on Go developers
using newer toolchains to compile old code.

A GODEBUG setting is a `key=value` pair

import java.util.PriorityQueue;
import java.util.Queue;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A double-ended priority queue, which provides constant-time access to both its least element and
 * its greatest element, as determined by the queue's specified comparator. If no comparator is

      delegate.cancel(mayInterruptIfRunning);
    }

    @Override
    public boolean isCancelled() {
      return delegate.isCancelled();
    }
  }

  /**
   * A {@link Scheduler} that provides a convenient way for the {@link AbstractScheduledService} to
   * use a dynamically changing schedule. After every execution of the task, assuming it hasn't been
   * cancelled, the {@link #getNextSchedule} method will be called.

    assertTrue(Arrays.equals(I18N.getBytes(UTF_8), Files.toByteArray(i18nFile)));
    assertTrue(Arrays.equals(I18N.getBytes(UTF_8), Files.asByteSource(i18nFile).read()));
  }

  /** A {@link File} that provides a specialized value for {@link File#length()}. */
  private static class BadLengthFile extends File {

    private final long badLength;

    public BadLengthFile(File delegate, long badLength) {

import java.util.function.Supplier;
import java.util.function.ToIntFunction;
import java.util.stream.Collector;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Provides static utility methods for creating and working with {@link Multiset} instances.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/CollectionUtilitiesExplained#multisets">{@code

import java.util.function.Supplier;
import java.util.function.ToIntFunction;
import java.util.stream.Collector;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Provides static utility methods for creating and working with {@link Multiset} instances.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/CollectionUtilitiesExplained#multisets">{@code

 *   <li>{@link StandardCharsets#US_ASCII} specifies the {@code Charset} of ASCII characters.
 *   <li>{@link CharMatcher#ascii} matches ASCII characters and provides text processing methods
 *       which operate only on the ASCII characters of a string.
 * </ul>
 *
 * @author Catherine Berry
 * @author Gregory Kick
 * @since 7.0
 */
@GwtCompatible

import java.util.List;
import java.util.Spliterator;
import java.util.function.Consumer;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Provides static methods for working with {@code Collection} instances.
 *
 * <p><b>Java 8+ users:</b> several common uses for this class are now more comprehensively

 * (note: even fixed-length splitters).
 *
 * <p>Splitter instances are thread-safe immutable, and are therefore safe to store as {@code static
 * final} constants.
 *
 * <p>The {@link Joiner} class provides the inverse operation to splitting, but note that a
 * round-trip between the two should be assumed to be lossy.
 *
 * <p>See the Guava User Guide article on <a

// used.
type Value struct {
	value interface{}
}

// Missing is used to indicate a non-existing value.
type Missing struct{}

// MarshalJSON provides json marshaling of values.
func (v Value) MarshalJSON() ([]byte, error) {
	if b, ok := v.ToBytes(); ok {
		return b, nil
	}
	return json.Marshal(v.value)
}