import java.util.Iterator;
import java.util.NoSuchElementException;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Note this class is a copy of {@link com.google.common.collect.AbstractIterator} (for dependency
 * reasons).
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

import java.util.Iterator;
import java.util.NoSuchElementException;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Note this class is a copy of {@link com.google.common.collect.AbstractIterator} (for dependency
 * reasons).
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

    DONE,

    /** We've suffered an exception and are kaput. */
    FAILED,
  }

  @CheckForNull private T next;

  /**
   * Returns the next element. <b>Note:</b> the implementation must call {@link #endOfData()} when
   * there are no elements left in the iteration. Failure to do so could result in an infinite loop.
   *

    DONE,

    /** We've suffered an exception and are kaput. */
    FAILED,
  }

  @CheckForNull private T next;

  /**
   * Returns the next element. <b>Note:</b> the implementation must call {@link #endOfData()} when
   * there are no elements left in the iteration. Failure to do so could result in an infinite loop.
   *