# Tutorial - User Guide { #tutorial-user-guide }

This tutorial shows you how to use **FastAPI** with most of its features, step by step.

Each section gradually builds on the previous ones, but it's structured to separate topics, so that you can go directly to any specific one to solve your specific API needs.

It is also built to work as a future reference so you can come back and see exactly what you need.

## Run the code { #run-the-code }

    @CsvSource({ "-1,Connection refused", "0x80,Not listening on called name", "0x81,Not listening for calling name",
            "0x82,Called name not present", "0x83,Called name present, but insufficient resources", "0x8F,Unspecified error",
            "999,Unknown error code: 999" })
    @DisplayName("getErrorString for SSN service errors")
    void testSessionServiceErrors(int errorCode, String description) {

        assertEquals(0, (dst[5] << 8) | (dst[4] & 0xFF));
    }

    @Test
    void testWriteDataWireFormat() {
        // Given
        // writeInt8 writes 8 bytes but needs to access dst[dstIndex+7]
        // Total bytes written: 8+8+8+8+2+6=40
        // But writeInt8 at position 34 needs to access position 34+7=41
        // So we need at least 42 bytes in the array
        byte[] dst = new byte[42];

        // When

## Wildcards { #wildcards }

It's also possible to declare the list as `"*"` (a "wildcard") to say that all are allowed.

But that will only allow certain types of communication, excluding everything that involves credentials: Cookies, Authorization headers like those used with Bearer Tokens, etc.

    }
    return builder().addAll(values).build();
  }

  /**
   * Returns an immutable array containing all the values from {@code stream}, in order.
   *
   * @since 33.4.0 (but since 22.0 in the JRE flavor)
   */
  @IgnoreJRERequirement // Users will use this only if they're already using streams.
  public static ImmutableLongArray copyOf(LongStream stream) {

   *
   * @since 22.0 (but only since 33.4.0 in the Android flavor)
   */
  public void forEach(IntConsumer consumer) {
    checkNotNull(consumer);
    for (int i = start; i < end; i++) {
      consumer.accept(array[i]);
    }
  }

  /**
   * Returns a stream over the values in this array, in order.
   *
   * @since 22.0 (but only since 33.4.0 in the Android flavor)
   */

"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

   * font/woff} to be the correct media type for WOFF, but this may be necessary in certain
   * situations for compatibility.
   *
   * @since 17.0
   */
  public static final MediaType WOFF = createConstant(APPLICATION_TYPE, "font-woff");

  /**
   * <a href="https://tools.ietf.org/html/rfc8081">RFC 8081</a> declares {@link #FONT_WOFF2
   * font/woff2} to be the correct media type for WOFF2, but this may be necessary in certain

// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//