* `Optional`
* ...and others.

////

//// tab | Python 3.8+

* `List`
* `Tuple`
* `Set`
* `Dict`
* `Union`
* `Optional`
* ...and others.

////

### Classes as types { #classes-as-types }

You can also declare a class as the type of a variable.

Let's say you have a class `Person`, with a name:

{* ../../docs_src/python_types/tutorial010.py hl[1:3] *}

    writing it has test supersource but no prod supersource.

    GWT happens to use the prod .gwt.xml, so it looks for no supersource for
    tests, either. This causes it to fail to find AtomicLongMapTest.

    Our workaround is to tell GWT that util.concurrent and all other packages
    have prod supersource, even if they have none. GWT is happy to ignore us

import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Map;
import java.util.Set;

/**
 * Optional features of classes derived from {@code Map}.
 *
 * @author George van den Driessche
 */
@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible
public enum MapFeature implements Feature<Map> {

        features down to compact but powerful abstractions, and controlling feature bloat carefully.

  - type: textarea
    attributes:
      label: API(s)
      description: Which existing classes or methods do you want to improve?
      placeholder: e.g., `com.google.common.collect.ImmutableList::of`
      render: java
    validations:
      required: true

  - type: textarea
    attributes:

        @Test
        @DisplayName("Null delegate causes NullPointerException during construction")
        void nullDelegate_throwsNPE() throws Exception {
            SmbFile parent = newParent();
            assertThrows(NullPointerException.class, () -> new ShareEnumIterator(parent, null, null));
        }

        @Test
        @DisplayName("Null parent with non-empty iterator causes NullPointerException during adapt")

    assertSame(EXCEPTION, record.getThrown());
  }

  public void testConcurrentModification() throws Exception {
    // Tests for the absence of a bug where logging while iterating over the
    // stored log records causes a ConcurrentModificationException
    assertTrue(handler.getStoredLogRecords().isEmpty());
    ExampleClassUnderTest.foo();
    ExampleClassUnderTest.foo();
    for (LogRecord unused : handler.getStoredLogRecords()) {

        }
    }

    @Nested
    @DisplayName("Inheritance verification")
    class InheritanceVerification {

        @Test
        @DisplayName("should properly extend base classes")
        void testInheritance() {
            // Arrange
            SamrPolicyHandle ph = createMockPolicyHandle();

            // Act

    }

    // Test command list construction with target classes directory
    public void test_executeSuggestCreator_withTargetClassesDir() {
        createRequiredDirectories();
        File targetDir = new File(System.getProperty("user.dir"), "target");
        File targetClassesDir = new File(targetDir, "classes");
        targetClassesDir.mkdirs();

        mockProcessHelper.setExitValue(0);

## Dependencias con parámetros

Todas las dependencias que hemos visto son una función o clase fija.

Pero podría haber casos en los que quieras poder establecer parámetros en la dependencia, sin tener que declarar muchas funciones o clases diferentes.

Imaginemos que queremos tener una dependencia que revise si el parámetro de query `q` contiene algún contenido fijo.

Pero queremos poder parametrizar ese contenido fijo.

## Una *instance* "callable"

 * appropriate primitive specialization such as {@code IntSupplier}) instead whenever possible.
 * Otherwise, at least reduce <i>explicit</i> dependencies on this type by using lambda expressions
 * or method references instead of classes, leaving your code easier to migrate in the future.
 *
 * <p>To use an existing supplier instance (say, named {@code supplier}) in a context where the