Preconditions.checkNotNull(valueEquivalence);

    Map<K, V> onlyOnLeft = new LinkedHashMap<>();
    Map<K, V> onlyOnRight = new LinkedHashMap<>(right); // will whittle it down
    Map<K, V> onBoth = new LinkedHashMap<>();
    Map<K, ValueDifference<V>> differences = new LinkedHashMap<>();
    doDifference(left, right, valueEquivalence, onlyOnLeft, onlyOnRight, onBoth, differences);

    Preconditions.checkNotNull(valueEquivalence);

    Map<K, V> onlyOnLeft = new LinkedHashMap<>();
    Map<K, V> onlyOnRight = new LinkedHashMap<>(right); // will whittle it down
    Map<K, V> onBoth = new LinkedHashMap<>();
    Map<K, ValueDifference<V>> differences = new LinkedHashMap<>();
    doDifference(left, right, valueEquivalence, onlyOnLeft, onlyOnRight, onBoth, differences);

  private final LittleEndianDataOutputStream out = new LittleEndianDataOutputStream(baos);

  public void testWriteLittleEndian() throws IOException {

    /* Write out various test values in LITTLE ENDIAN FORMAT */
    out.write(new byte[] {-100, 100});
    out.writeBoolean(true);
    out.writeBoolean(false);
    out.writeByte(100);
    out.writeByte(-100);
    out.writeByte((byte) 200);
    out.writeChar('a');

  private final LittleEndianDataOutputStream out = new LittleEndianDataOutputStream(baos);

  public void testWriteLittleEndian() throws IOException {

    /* Write out various test values in LITTLE ENDIAN FORMAT */
    out.write(new byte[] {-100, 100});
    out.writeBoolean(true);
    out.writeBoolean(false);
    out.writeByte(100);
    out.writeByte(-100);
    out.writeByte((byte) 200);
    out.writeChar('a');

  }

  public void testReadLittleEndian() throws IOException {
    DataInput in = new LittleEndianDataInputStream(new ByteArrayInputStream(data));

    /* Read in various values in LITTLE ENDIAN FORMAT */
    byte[] b = new byte[2];
    in.readFully(b);
    assertEquals(-100, b[0]);
    assertEquals(100, b[1]);
    assertEquals(true, in.readBoolean());
    assertEquals(false, in.readBoolean());

<img src="/img/tutorial/security/image01.png">

/// check | Authorize button!

You already have a shiny new "Authorize" button.

And your *path operation* has a little lock in the top-right corner that you can click.

///

And if you click it, you have a little authorization form to type a `username` and `password` (and other optional fields):

<img src="/img/tutorial/security/image02.png">

/// note

   * compatible pure-Java fallback.
   */
  private static final LittleEndianBytes byteArray = makeGetter();

  /**
   * Load 8 bytes into long in a little endian manner, from the substring between position and
   * position + 8. The array must have at least 8 bytes from offset (inclusive).
   *
   * @param input the input bytes

Some time ago, [a **FastAPI** user asked](https://github.com/fastapi/fastapi/issues/3#issuecomment-454956920):

> What’s the history of this project? It seems to have come from nowhere to awesome in a few weeks [...]

Here's a little bit of that history.

## Alternatives { #alternatives }

```

</div>

It is **HIGHLY encouraged** that you write or copy the code, edit it and run it locally.

Using it in your editor is what really shows you the benefits of FastAPI, seeing how little code you have to write, all the type checks, autocompletion, etc.

---

## Install FastAPI { #install-fastapi }

The first step is to install FastAPI.

If you want to:

* declare the `q` query parameter without a `Query` nor any default value
* declare the path parameter `item_id` using `Path`
* have them in a different order
* not use `Annotated`

...Python has a little special syntax for that.

Pass `*`, as the first parameter of the function.