*
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/PrimitivesExplained#unsigned-support">unsigned
 * primitive utilities</a>.
 *
 * @author Louis Wasserman
 * @author Colin Evans
 * @since 11.0
 */
@GwtCompatible(serializable = true)
@ElementTypesAreNonnullByDefault

import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Queue;
import java.util.Set;

/**
 * Utilities for collecting and validating tester requirements from annotations.
 *
 * @author George van den Driessche
 */
@GwtIncompatible
public final class FeatureUtil {

 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/PrimitivesExplained#unsigned-support">unsigned
 * primitive utilities</a>.
 *
 * @author Louis Wasserman
 * @author Colin Evans
 * @since 11.0
 */
@GwtCompatible(serializable = true)
@ElementTypesAreNonnullByDefault

      checkValidState(cache);

      assertThrows(NullPointerException.class, () -> entry.setValue(null));
      checkValidState(cache);
    }
  }

  /* ---------------- Local utilities -------------- */

  /** Most of the tests in this class run against every one of these caches. */
  private Iterable<LoadingCache<Object, Object>> caches() {
    // lots of different ways to configure a LoadingCache

import java.util.function.ToIntFunction;
import java.util.stream.Collector;
import java.util.stream.Stream;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/** Collectors utilities for {@code common.collect} internals. */
@GwtCompatible
@ElementTypesAreNonnullByDefault
@SuppressWarnings("Java7ApiChecker")
@IgnoreJRERequirement // used only from APIs with Java 8 types in them

It's common that each authentication provider names their flows in a different way, to make it part of their brand.

But in the end, they are implementing the same OAuth2 standard.

///

**FastAPI** includes utilities for all these OAuth2 authentication flows in `fastapi.security.oauth2`.

## `Security` in decorator `dependencies`

{!../../docs_src/handling_errors/tutorial002.py!}
```

## Install custom exception handlers

You can add custom exception handlers with <a href="https://www.starlette.io/exceptions/" class="external-link" target="_blank">the same exception utilities from Starlette</a>.

Let's say you have a custom exception `UnicornException` that you (or a library you use) might `raise`.

And you want to handle this exception globally with FastAPI.

import java.util.concurrent.TimeoutException;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Utilities for treating interruptible operations as uninterruptible. In all cases, if a thread is
 * interrupted during such a call, the call continues to block until the result is available or the

import java.util.regex.Pattern;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Supplies an arbitrary "default" instance for a wide range of types, often useful in testing
 * utilities.
 *
 * <p>Covers arrays, enums and common types defined in {@code java.lang}, {@code java.lang.reflect},
 * {@code java.io}, {@code java.nio}, {@code java.math}, {@code java.util}, {@code

import java.util.Collection;
import java.util.Map.Entry;
import java.util.concurrent.atomic.AtomicReference;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Utilities for working with {@link Type}.
 *
 * @author Ben Yu
 */
@ElementTypesAreNonnullByDefault
final class Types {

  /** Class#toString without the "class " and "interface " prefixes */