private transient volatile @Nullable CacheEntry<K, V> cacheEntry2;

  MapRetrievalCache(Map<K, V> backingMap) {
    super(backingMap);
  }

  @SuppressWarnings("unchecked") // Safe because we only cast if key is found in map.
  @Override
  @Nullable V get(Object key) {
    checkNotNull(key);
    V value = getIfCached(key);
    if (value != null) {
      return value;
    }

    value = getWithoutCaching(key);

    void testToInetAddressWithException() throws UnknownHostException {
        // Given
        when(mockAddress.toInetAddress()).thenThrow(new UnknownHostException("Host not found"));

        // When & Then
        assertThrows(UnknownHostException.class, () -> {
            mockAddress.toInetAddress();
        }, "Should propagate UnknownHostException");
    }

    @Test

// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package lex

import (
	"go/build/constraint"
	"io"
	"os"
	"strings"
	"text/scanner"
	"unicode"

	"cmd/asm/internal/flags"
	"cmd/internal/objabi"
	"cmd/internal/src"
)

// A Tokenizer is a simple wrapping of text/scanner.Scanner, configured

    /**
     * Retrieves an integer value from system properties with a default fallback.
     *
     * @param key the property key to look up
     * @param defaultValue the default value if the property is not found or invalid
     * @return the integer value or default value
     */
    protected Integer getDefaultInteger(final String key, final Integer defaultValue) {
        final String value = systemProperties.getProperty(key);

```

Mas se o cliente faz uma requisição para `http://example.com/items/bar` (ou seja, um não existente `item_id "bar"`), esse cliente receberá um HTTP status code 404 (o erro "não encontrado" — *not found error*), e uma resposta JSON:

```JSON
{
  "detail": "Item not found"
}
```

/// tip | Dica

Quando você lançar um `HTTPException`, você pode passar qualquer valor convertível em JSON como parâmetro de `detail`, e não apenas `str`.

			// actions accordingly.
			// nolint:gocritic
			if result.Item.IsLatest {
				var match BatchJobExpireFilter
				var found bool
				for _, rule := range r.Rules {
					if rule.Matches(result.Item, now) {
						match = rule
						found = true
						break
					}
				}
				if !found {
					continue
				}

				if prevObj.Name != result.Item.Name {
					// switch the object
					pushToExpire()

                    HtmlNext htmlNext = (HtmlNext) field.get(null);
                    String path = htmlNext.getRoutingPath();
                    assertFalse("Duplicate path found: " + path + " in field " + field.getName(), paths.contains(path));
                    paths.add(path);
                }
            }
        }
        assertTrue("Should have unique paths", paths.size() > 0);
    }

    /**
     * Gets the singleton instance of the XmlService.
     *
     * @return the XmlService instance
     * @throws IllegalStateException if no implementation is found
     */
    private static XmlService getService() {
        return Holder.INSTANCE;
    }

    /** Holder class for lazy initialization of the default instance */
    private static final class Holder {

Они похожи на двухсотые HTTP статус-коды (от 200 до 299), которые означают, что запрос обработан успешно.

Четырёхсотые статус-коды означают, что ошибка произошла по вине клиента.

Помните ли ошибки **"404 Not Found "** (и шутки) ?

## Использование `HTTPException`

Для возврата клиенту HTTP-ответов с ошибками используется `HTTPException`.

### Импортируйте `HTTPException`

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

</div>

すると、以下のように `/openapi.json`, `/docs`, `/redoc` のどのURLにアクセスしても、 `404 Not Found` エラーが返ってくるようになります。

```JSON
{
    "detail": "Not Found"
}