* href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
 * default} methods. Instead, it inherits their default implementations. When those implementations
 * invoke methods, they invoke methods on the {@code ForwardingListeningExecutorService}.
 *
 * @author Isaac Shum
 * @since 10.0
 */
@J2ktIncompatible

   * @return {@code string} if it is not null; {@code ""} otherwise
   */
  static String nullToEmpty(@Nullable String string) {
    return (string == null) ? "" : string;
  }

  /**
   * Returns the string if it is not empty, or a null string otherwise.
   *
   * @param string the string to test and possibly return
   * @return {@code string} if it is not empty; {@code null} otherwise
   */

 * Outer class that exists solely to let us write {@code Partially.GwtIncompatible} instead of plain
 * {@code GwtIncompatible}. This is more accurate for {@link Futures#catching}, which is available
 * under GWT but with a slightly different signature.
 *
 * <p>We can't use {@code PartiallyGwtIncompatible} because then the GWT compiler wouldn't recognize
 * it as a {@code GwtIncompatible} annotation. And for {@code Futures.catching}, we need the GWT

        sink.writeUtf8(requestMethod).writeByte('\n'.code)
        sink.writeDecimalLong(varyHeaders.size.toLong()).writeByte('\n'.code)
        for (i in 0 until varyHeaders.size) {
          sink
            .writeUtf8(varyHeaders.name(i))
            .writeUtf8(": ")
            .writeUtf8(varyHeaders.value(i))
            .writeByte('\n'.code)
        }

 * implement it:
 *
 * {@snippet :
 * // won't work
 * TreeTraverser<NodeType> traverser = node -> node.getChildNodes();
 * }
 *
 * Instead, you can pass a lambda expression to the {@code using} factory method:
 *
 * {@snippet :
 * TreeTraverser<NodeType> traverser = TreeTraverser.using(node -> node.getChildNodes());
 * }
 *
 * @author Louis Wasserman
 * @since 15.0

   * it does not, then null is returned. If it does, then if {@code throwIfDuplicateKeys} is true an
   * {@code IllegalArgumentException} is thrown, and otherwise the existing {@link Entry} is
   * returned.
   *
   * @throws IllegalArgumentException if another entry in the bucket has the same key and {@code
   *     throwIfDuplicateKeys} is true

    this(chunkSize, chunkSize);
  }

  /**
   * Constructor for use by subclasses. This hasher instance will process chunks of the specified
   * size, using an internal buffer of {@code bufferSize} size, which must be a multiple of {@code
   * chunkSize}.
   *
   * @param chunkSize the number of bytes available per {@link #process(ByteBuffer)} invocation;
   *     must be at least 4

   *
   * Note that transport-layer success (receiving a HTTP response code, headers and body) does not
   * necessarily indicate application-layer success: `response` may still indicate an unhappy HTTP
   * response code like 404 or 500.
   *
   * @throws IOException if the request could not be executed due to cancellation, a connectivity

 *
 * @author Ben Yu
 */
@GwtIncompatible
@J2ktIncompatible
@NullMarked
abstract class DummyProxy {

  /**
   * Returns a new proxy for {@code interfaceType}. Proxies of the same interface are equal to each
   * other if the {@link DummyProxy} instance that created the proxies are equal.
   */
  final <T> T newProxy(TypeToken<T> interfaceType) {

///

## 프로젝트 생성

먼저, 프로젝트를 위한 디렉터리를 하나 생성합니다.

보통 사용자 홈 디렉터리 안에 `code`라는 디렉터리를 만들고, 그 안에 프로젝트마다 하나씩 디렉터리를 만들어 관리합니다.

<div class="termy">

```console
// 홈 디렉터리로 이동
$ cd
// 모든 코드 프로젝트를 위한 디렉터리 생성
$ mkdir code
// code 디렉터리로 이동
$ cd code
// 이번 프로젝트를 위한 디렉터리 생성
$ mkdir awesome-project
// 해당 프로젝트 디렉터리로 이동
$ cd awesome-project
```

</div>