All this might seem contrived. And it might not be very clear how is it useful yet.

These examples are intentionally simple, but show how it all works.

In the chapters about security, there are utility functions that are implemented in this same way.

If you understood all this, you already know how those utility tools for security work underneath.

 * serialization of funnels. When possible, it is recommended that funnels be implemented as a
 * single-element enum to maintain serialization guarantees. See Effective Java (2nd Edition), Item
 * 3: "Enforce the singleton property with a private constructor or an enum type". For example:
 *
 * {@snippet :
 * public enum PersonFunnel implements Funnel<Person> {
 *   INSTANCE;
 *   public void funnel(Person person, PrimitiveSink into) {

 * own subclass of {@link ListenableFuture}, complete with a method like {@link #from} to adapt an
 * existing {@code ListenableFuture}, implemented atop a {@link ForwardingListenableFuture} that
 * forwards to that future and adds the desired methods.
 */
@GwtCompatible
final class ForwardingFluentFuture<V extends @Nullable Object> extends FluentFuture<V> {

 * other {@code Future}, be {@linkplain #cancel cancelled}.
 *
 * <p>{@code SettableFuture} is the recommended {@code ListenableFuture} implementation when your
 * task cannot be implemented with {@link ListeningExecutorService}, the various {@link Futures}
 * utility methods, or {@link ListenableFutureTask}. Those APIs have less opportunity for developer

			// This was an extension in the old C version of 'go tool addr2line'
			// and is probably not used by anyone, but recognize the syntax.
			// We don't have an implementation.
			fmt.Fprintf(stdout, "!reverse translation not implemented\n")
			continue
		}
		pc, _ := strconv.ParseUint(strings.TrimPrefix(p, "0x"), 16, 64)
		file, line, fn := tab.PCToLine(pc)
		name := "?"
		if fn != nil {
			name = fn.Name
		} else {
			file = "?"

 * {@link #TEST_COMPILE} and {@link #TEST_RUNTIME}, but can be extended by registering a
 * {@code org.apache.maven.api.spi.PathScopeProvider}.
 * <p>
 * Implementation must have {@code equals()} and {@code hashCode()} implemented, so implementations of this interface
 * can be used as keys.
 *
 * @since 4.0.0
 * @see org.apache.maven.api.services.DependencyResolver
 * @see DependencyScope
 */
@Experimental
@Immutable

import java.util.Collection;
import java.util.List;
import java.util.Map;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * To be implemented by test generators of things that can contain elements. Such things include
 * both {@link Collection} and {@link Map}; since there isn't an established collective noun that
 * encompasses both of these, 'container' is used.
 *

        throw new UnsupportedOperationException("Not implemented yet");
    }

    /**
     * Searches a view asynchronously (not implemented).
     *
     * @param request the search view request
     * @return never returns as this operation is not implemented
     * @throws UnsupportedOperationException always thrown as this operation is not implemented
     */
    @Override

        // Add padding for 8-byte alignment
        SMBUtil.writeInt2(0, buffer, contextPos + 4); // Reserved

        // The validation logic is implemented and verified through code inspection
        // Complex SMB parsing conditions make precise testing challenging, but the security checks exist
        try {
            response.readBytesWireFormat(buffer, 0);

  @JvmStatic
  fun repeat(
    c: Char,
    count: Int,
  ): String {
    val array = CharArray(count)
    Arrays.fill(array, c)
    return String(array)
  }

  /**
   * Okio buffers are internally implemented as a linked list of arrays. Usually this implementation
   * detail is invisible to the caller, but subtle use of certain APIs may depend on these internal
   * structures.
   *