import static com.google.common.collect.testing.testers.ReflectionFreeAssertThrows.assertThrows;

import com.google.common.annotations.GwtCompatible;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests {@code get()} operations on a list. Can't be invoked directly;
 * please see {@link com.google.common.collect.testing.ListTestSuiteBuilder}.
 *
 * @author Chris Povirk
 */
@GwtCompatible

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.testing.AbstractMapTester;
import com.google.common.collect.testing.features.CollectionSize;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests {@code isEmpty()} operations on a map. Can't be invoked
 * directly; please see {@link com.google.common.collect.testing.MapTestSuiteBuilder}.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible

```

`Optional[str]`을 `str` 대신 쓰게 되면, 특정 값이 실제로는 `None`이 될 수도 있는데 항상 `str`이라고 가정하는 상황에서 에디터가 에러를 찾게 도와줄 수 있습니다.

#### Generic(제네릭) 타입

이 타입은 대괄호 안에 매개변수를 가지며, 종류는:

* `List`
* `Tuple`
* `Set`
* `Dict`
* `Optional`
* ...등등

위와 같은 타입은 **Generic(제네릭) 타입** 혹은 **Generics(제네릭스)**라고 불립니다.

### 타입으로서의 클래스

변수의 타입으로 클래스를 선언할 수도 있습니다.

이름(name)을 가진 `Person` 클래스가 있다고 해봅시다.

import kotlin.contracts.contract
import okhttp3.Dispatcher
import okhttp3.internal.http2.Http2Connection
import okhttp3.internal.http2.Http2Stream
import okhttp3.internal.http2.Http2Writer

/**
 * Centralisation of central locks according to docs/contribute/concurrency.md
 */
internal object Locks {
  inline fun <T> Dispatcher.withLock(action: () -> T): T {
    contract { callsInPlace(action, InvocationKind.EXACTLY_ONCE) }

[![Java CI with Maven](https://github.com/codelibs/fess/actions/workflows/maven.yml/badge.svg)](https://github.com/codelibs/fess/actions/workflows/maven.yml)
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[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://github.com/gitbucket/gitbucket/blob/master/LICENSE)

[![Java CI with Maven](https://github.com/codelibs/fess/actions/workflows/maven.yml/badge.svg)](https://github.com/codelibs/fess/actions/workflows/maven.yml)
[![Maven Central](https://maven-badges.herokuapp.com/maven-central/org.codelibs.fess/fess/badge.svg)](https://maven-badges.herokuapp.com/maven-central/org.codelibs.fess/fess)
[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://github.com/gitbucket/gitbucket/blob/master/LICENSE)

import com.google.common.collect.Multiset;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.testing.SerializableTester;
import java.util.Set;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests multiset-specific serialization. Can't be invoked directly;
 * please see {@link MultisetTestSuiteBuilder}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible // but no-op

import com.google.common.collect.testing.AbstractCollectionTester;
import com.google.common.collect.testing.Helpers;
import com.google.common.collect.testing.features.CollectionFeature;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests {@code stream} operations on a collection. Can't be invoked
 * directly; please see {@link com.google.common.collect.testing.CollectionTestSuiteBuilder}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.CollectionSize;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests remove operations on a set. Can't be invoked directly; please
 * see {@link com.google.common.collect.testing.ListTestSuiteBuilder}.
 *
 * @author George van den Driessche
 */
@GwtCompatible

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.CollectionSize;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests remove operations on a set. Can't be invoked directly; please
 * see {@link com.google.common.collect.testing.ListTestSuiteBuilder}.
 *
 * @author George van den Driessche
 */
@GwtCompatible