arraycopy(array, 0, dst, dstOff, size);
    return dstOff + size;
  }

  // The fake cast to E is safe because the creation methods only allow E's
  @Override
  @SuppressWarnings("unchecked")
  public E get(int index) {
    checkElementIndex(index, size);
    // requireNonNull is safe because we guarantee that the first `size` elements are non-null.
    return (E) requireNonNull(array[index]);
  }

 * useForNull} has no effect on the instance it is invoked on! You must store and use the new joiner
 * instance returned by the method. This makes joiners thread-safe, and safe to store as {@code
 * static final} constants.
 *
 * {@snippet :
 * // Bad! Do not do this!
 * Joiner joiner = Joiner.on(',');
 * joiner.skipNulls(); // does nothing!
 * return joiner.join("wrong", null, "wrong");

  boolean isEmpty() {
    // The casts are safe because of the has*Bound() checks.
    return (hasUpperBound() && tooLow(uncheckedCastNullableTToT(getUpperEndpoint())))
        || (hasLowerBound() && tooHigh(uncheckedCastNullableTToT(getLowerEndpoint())));
  }

  boolean tooLow(@ParametricNullness T t) {
    if (!hasLowerBound()) {
      return false;
    }
    // The cast is safe because of the hasLowerBound() check.

 * invoke methods, they invoke methods on the {@code ForwardingSet}.
 *
 * <p>The {@code standard} methods are not guaranteed to be thread-safe, even when all of the
 * methods that they depend on are thread-safe.
 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible

  /**
   * {@inheritDoc}
   *
   * <p>All elements in the returned list must be {@link ListenableFuture} instances. The easiest
   * way to obtain a {@code List<ListenableFuture<T>>} from this method is an unchecked (but safe)
   * cast:
   *
   * <pre>
   *   {@code @SuppressWarnings("unchecked") // guaranteed by invokeAll contract}
   *   {@code List<ListenableFuture<T>> futures = (List) executor.invokeAll(tasks);}
   * </pre>
   *

      keyList.count = 0;
      modCount++;
    } else {
      // requireNonNull is safe (under the conditions listed in the comment in the branch above).
      KeyList<K, V> keyList = requireNonNull(keyToKeyList.get(node.getKey()));
      keyList.count--;

      if (node.previousSibling == null) {
        // requireNonNull is safe because we checked that not *both* siblings were null.

    }
  }

  /** Returns a fresh {@link InternerBuilder} instance. */
  public static InternerBuilder newBuilder() {
    return new InternerBuilder();
  }

  /**
   * Returns a new thread-safe interner which retains a strong reference to each instance it has
   * interned, thus preventing these instances from being garbage-collected. If this retention is

      bufferSize = 1;
    } else if (bufferSize < k) {
      buffer[bufferSize++] = elem;
      // uncheckedCastNullableTToT is safe because bufferSize > 0.
      if (comparator.compare(elem, uncheckedCastNullableTToT(threshold)) > 0) {
        threshold = elem;
      }
      // uncheckedCastNullableTToT is safe because bufferSize > 0.
    } else if (comparator.compare(elem, uncheckedCastNullableTToT(threshold)) < 0) {

    C columnKey = columnKeySet().asList().get(columnIndex);
    // requireNonNull is safe because we use indexes that were populated by the constructor.
    V value = requireNonNull(values[rowIndex][columnIndex]);
    return cellOf(rowKey, columnKey, value);
  }

  @Override
  V getValue(int index) {
    // requireNonNull is safe because we use indexes that were populated by the constructor.

import org.commonmark.parser.Parser;
import org.commonmark.renderer.html.HtmlRenderer;
import org.owasp.html.HtmlPolicyBuilder;
import org.owasp.html.PolicyFactory;

/**
 * Renders markdown to sanitized HTML for safe display in the chat interface.
 * Uses commonmark for markdown parsing and OWASP HTML Sanitizer for XSS prevention.
 */
public class MarkdownRenderer {