### Top-level application { #top-level-application }

First, create the main, top-level, **FastAPI** application, and its *path operations*:

{* ../../docs_src/sub_applications/tutorial001_py39.py hl[3, 6:8] *}

### Sub-application { #sub-application }

Then, create your sub-application, and its *path operations*.

This sub-application is just another standard FastAPI application, but this is the one that will be "mounted":

     */
    @Override
    public Iterator<E> iterator() {
        return map.keySet().iterator();
    }

    /**
     * Returns the number of elements in this set (its cardinality).
     *
     * @return the number of elements in this set (its cardinality).
     */
    @Override
    public int size() {
        return map.size();
    }

    /**
     * Returns true if this set contains no elements.
     *

    /**
     * Validate that the constructor masks the supplied value to its
     * lowest 8 bits (NdrShort incorrectly masks to 8 bits even though it's a short).
     */
    @ParameterizedTest
    @ValueSource(ints = { 0, 1, 255, -1, 256, 65535 })
    void constructorMasksValue(int input) {
        NdrShort ns = new NdrShort(input);
        // NdrShort masks to 0xFF (8 bits) in its constructor
        int expected = input & 0xFF;

                "org.apache.maven.its.plugins",
                "maven-it-plugin",
                "0.1",
                "compile",
                "jar",
                null,
                new DefaultArtifactHandler("ignore"));
        PluginDescriptor descriptor = new PluginDescriptor();
        descriptor.setGroupId("org.apache.maven.its.plugins");
        descriptor.setArtifactId("maven-it-plugin");

     * <li>If <code>type</code> is a parameterized type, its raw type is returned.</li>
     * <li>If <code>type</code> is a wildcard type, its (first) upper bound is returned.</li>
     * <li>If <code>type</code> is a type variable and is a key in the given map, its actual type argument is returned.</li>
     * <li>If <code>type</code> is a type variable and is not a key in the given map, its (first) upper bound is returned.</li>

            op.rangeSize(fessConfig.getPagingPageRangeSizeAsInteger());
        }).createPageNumberList());

        return fileConfigList;
    }

    /**
     * Deletes a file configuration and its associated authentication records.
     * This method removes the file configuration from the database and also
     * deletes all related file authentication entries.
     *

        // Verify field accessibility is restored to its original state
        boolean finalAccessibility = field.canAccess(bean);
        assertEquals(
                initialAccessibility,
                finalAccessibility,
                "Field accessibility should be restored to its original state after setting value");
    }

    @Test

## Using the `jsonable_encoder` in a `Response` { #using-the-jsonable-encoder-in-a-response }

Because **FastAPI** doesn't make any changes to a `Response` you return, you have to make sure its contents are ready for it.

For example, you cannot put a Pydantic model in a `JSONResponse` without first converting it to a `dict` with all the data types (like `datetime`, `UUID`, etc) converted to JSON-compatible types.

    }
    copyIntoArray(other, 0);
    return other;
  }

  /** If this collection is backed by an array of its elements in insertion order, returns it. */
  @Nullable Object @Nullable [] internalArray() {
    return null;
  }

  /**
   * If this collection is backed by an array of its elements in insertion order, returns the offset
   * where this collection's elements start.
   */
  int internalArrayStart() {

Use its [builder][handshake_certificates_builder] to define which certificates the HTTPS server
returns to its clients. The returned instance can create an `SSLSocketFactory` that implements this
policy:

```java
HandshakeCertificates serverCertificates = new HandshakeCertificates.Builder()
    .heldCertificate(localhostCertificate)
    .build();
MockWebServer server = new MockWebServer();