* times, due to numerical errors.
   *
   * <h3>Non-finite values</h3>
   *
   * <p>If the dataset contains any non-finite values ({@link Double#POSITIVE_INFINITY}, {@link
   * Double#NEGATIVE_INFINITY}, or {@link Double#NaN}) then the result is {@link Double#NaN}.
   *
   * @throws IllegalStateException if the dataset is empty
   */
  public double populationCovariance() {
    checkState(count() != 0);

import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * Most of the logic for {@link IteratorTester} and {@link ListIteratorTester}.
 *
 * @param <E> the type of element returned by the iterator
 * @param <I> the type of the iterator ({@link Iterator} or {@link ListIterator})
 * @author Kevin Bourrillion
 * @author Chris Povirk
 */
@GwtCompatible
@NullMarked

  private @Nullable ThreadFactory backingThreadFactory = null;

  /**
   * Creates a new {@link ThreadFactory} builder.
   *
   * <p><b>Java 21+ users:</b> use {@link Thread#ofPlatform()} instead, translating other calls on
   * the builder as documented on each method (except for the rarely used {@link #setThreadFactory},
   * which does not have an equivalent).
   */
  public ThreadFactoryBuilder() {}

  /**

    * <a href="https://fastapi.tiangolo.com/features/" class="external-link" target="_blank">**Et bien d'autres fonctionnalités**</a> comme la validation automatique, la sérialisation, l'authentification avec OAuth2 JWT tokens,...

import java.io.DataInput;
import java.io.DataInputStream;
import java.io.EOFException;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * An implementation of {@link DataInput} that uses little-endian byte ordering for reading {@code
 * short}, {@code int}, {@code float}, {@code double}, and {@code long} values.
 *

# CORS（跨域资源共享）

<a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS" class="external-link" target="_blank">CORS 或者「跨域资源共享」</a> 指浏览器中运行的前端拥有与后端通信的 JavaScript 代码，而后端处于与前端不同的「源」的情况。

## 源

源是协议（`http`，`https`）、域（`myapp.com`，`localhost`，`localhost.tiangolo.com`）以及端口（`80`、`443`、`8080`）的组合。

因此，这些都是不同的源：

* `http://localhost`
* `https://localhost`
* `http://localhost:8080`

即使它们都在 `localhost` 中，但是它们使用不同的协议或者端口，所以它们都是不同的「源」。

## 步骤

     * <p>
     * The list of {@link CoreExtensions} if present, is in precedence order.
     *
     * @return an {@link Optional} containing the {@link CoreExtensions}, or empty if not configured
     */
    @Nonnull
    Optional<List<CoreExtensions>> coreExtensions();

    /**
     * Returns detected CI system, if any.
     *

   * shortcut for creating an empty list then calling {@link Iterables#addAll}.
   *
   * <p><b>Note:</b> if mutability is not required and the elements are non-null, use {@link
   * ImmutableList#copyOf(Iterable)} instead. (Or, change {@code elements} to be a {@link
   * FluentIterable} and call {@code elements.toList()}.)
   *
   * <p><b>Performance note:</b> {@link ArrayList} and {@link java.util.ArrayDeque} consistently

    }
    return array;
  }

  /**
   * Returns a fixed-size list backed by the specified array, similar to {@link
   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
   * set a value to {@code null} will result in a {@link NullPointerException}.
   *
   * <p>The returned list maintains the values, but not the identities, of {@code Float} objects

 * A path scope is used to determine the kind of build or class path that will be built when resolving
 * dependencies using the {@link org.apache.maven.api.services.DependencyResolver} service.
 * <p>
 * This extensible enum has four defined values, {@link #MAIN_COMPILE}, {@link #MAIN_RUNTIME},
 * {@link #TEST_COMPILE} and {@link #TEST_RUNTIME}, but can be extended by registering a
 * {@code org.apache.maven.api.spi.PathScopeProvider}.
 * <p>