## Créer une instance { #create-an-instance }

Nous pouvons créer une instance de cette classe avec :

{* ../../docs_src/dependencies/tutorial011_an_py310.py hl[18] *}

Et de cette façon, nous pouvons « paramétrer » notre dépendance, qui contient maintenant « bar », en tant qu’attribut `checker.fixed_content`.

## Utiliser l'instance comme dépendance { #use-the-instance-as-a-dependency }

      @ParametricNullness T instance) {
    return new SupplierOfInstance<>(instance);
  }

  private static final class SupplierOfInstance<T extends @Nullable Object>
      implements Supplier<T>, Serializable {
    @ParametricNullness final T instance;

    SupplierOfInstance(@ParametricNullness T instance) {
      this.instance = instance;
    }

    @Override
    @ParametricNullness
    public T get() {

      @ParametricNullness T instance) {
    return new SupplierOfInstance<>(instance);
  }

  private static final class SupplierOfInstance<T extends @Nullable Object>
      implements Supplier<T>, Serializable {
    @ParametricNullness final T instance;

    SupplierOfInstance(@ParametricNullness T instance) {
      this.instance = instance;
    }

    @Override
    @ParametricNullness
    public T get() {

        // Act & Assert
        // unwrap to interface itself should return same instance
        CredentialsInternal unwrapped = creds.unwrap(CredentialsInternal.class);
        assertNotNull(unwrapped, "unwrap to CredentialsInternal returns instance");
        assertSame(creds, unwrapped, "unwrap returns the same object instance");

        // unwrap to unrelated type should return null (use another Credentials implementation)

   */
  @GwtIncompatible // Class.cast, Class.isInstance
  public static <X extends Throwable> void throwIfInstanceOf(
      Throwable throwable, Class<X> declaredType) throws X {
    checkNotNull(throwable);
    if (declaredType.isInstance(throwable)) {
      throw declaredType.cast(throwable);
    }
  }

  /**
   * Propagates {@code throwable} exactly as-is, if and only if it is an instance of {@code
   * declaredType}. Example usage:

    //                                                                           =========
    private static final DuplicateHostDbm _instance = new DuplicateHostDbm();

    private DuplicateHostDbm() {
    }

    public static DuplicateHostDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final RelatedQueryDbm _instance = new RelatedQueryDbm();

    private RelatedQueryDbm() {
    }

    public static RelatedQueryDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final RoleTypeDbm _instance = new RoleTypeDbm();

    private RoleTypeDbm() {
    }

    public static RoleTypeDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final PathMappingDbm _instance = new PathMappingDbm();

    private PathMappingDbm() {
    }

    public static PathMappingDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

internal fun <T> readFieldOrNull(
  instance: Any,
  fieldType: Class<T>,
  fieldName: String,
): T? {
  var c: Class<*> = instance.javaClass
  while (c != Any::class.java) {
    try {
      val field = c.getDeclaredField(fieldName)
      field.isAccessible = true
      val value = field.get(instance)
      return if (!fieldType.isInstance(value)) null else fieldType.cast(value)