Description: `set the acceptable quorum expected for list operations e.g. "optimal", "reduced", "disk", "strict", "auto"` + defaultHelpPostfix(apiListQuorum),
			Optional:    true,
			Type:        "string",
		},
		config.HelpKV{
			Key:         apiReplicationPriority,
			Description: `set replication priority` + defaultHelpPostfix(apiReplicationPriority),
			Optional:    true,
			Type:        "string",
		},
		config.HelpKV{

    throw new IllegalStateException("Optional.get() cannot be called on an absent value");
  }

  @Override
  public T or(T defaultValue) {
    return checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)");
  }

  @SuppressWarnings("unchecked") // safe covariant cast
  @Override
  public Optional<T> or(Optional<? extends T> secondChoice) {
    return (Optional<T>) checkNotNull(secondChoice);
  }

  source:
    type: minio # valid values are "s3" or "minio"
    bucket: mytest
    prefix: object-prefix1 # 'PREFIX' is optional
    # If your source is the 'local' alias specified to 'mc batch start', then the 'endpoint' and 'credentials' fields are optional and can be omitted
    # Either the 'source' or 'remote' *must* be the "local" deployment
#    endpoint: "http://127.0.0.1:9000"

     * @return an {@link Optional} containing the boolean value {@code true} if specified, or empty
     */
    @Nonnull
    Optional<Boolean> plugins();

    /**
     * Should apply all upgrade options (equivalent to --model-version 4.1.0 --infer --model --plugins).
     * This is a convenience option that combines model upgrade, inference, compatibility fixes, and plugin upgrades.
     *

     *
     * @return An Optional containing the lowest matching version, or empty Optional if no versions
     *         matched the requested range
     */
    @Nonnull
    default Optional<Version> getLowestVersion() {
        return getVersions().isEmpty()
                ? Optional.empty()
                : Optional.of(getVersions().get(0));
    }

    /**

@REM
@REM   JAVA_HOME           (Optional) Points to a Java installation.
@REM   MAVEN_BATCH_ECHO    (Optional) Set to 'on' to enable the echoing of the batch commands.
@REM   MAVEN_BATCH_PAUSE   (Optional) set to 'on' to wait for a key stroke before ending.
@REM   MAVEN_OPTS          (Optional) Java runtime options used when Maven is executed.
@REM   MAVEN_SKIP_RC       (Optional) Flag to disable loading of mavenrc files.

			Optional:    true,
			Type:        "csv",
		},
		config.HelpKV{
			Key:         AllowEncrypted,
			Description: `enable 'encryption' along with compression`,
			Optional:    true,
			Type:        "on|off",
		},
		config.HelpKV{
			Key:         config.Comment,
			Description: config.DefaultComment,
			Optional:    true,
			Type:        "sentence",
		},
	}

        return of(active, optional, true);
    }

    static ActivationSettings of(final boolean active, final boolean optional, final boolean recursive) {
        return new ActivationSettings(active, optional, recursive);
    }

    static ActivationSettings activated() {
        return new ActivationSettings(true, false, true);
    }

    static ActivationSettings activatedOpt() {

  @Override
  public T get() {
    return reference;
  }

  @Override
  public T or(T defaultValue) {
    checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)");
    return reference;
  }

  @Override
  public Optional<T> or(Optional<? extends T> secondChoice) {
    checkNotNull(secondChoice);
    return this;
  }

  @Override
  public T or(Supplier<? extends T> supplier) {

两者是等价的，底层其实也是一样的。但我更推荐使用 `Union` 而不是 `Optional`，因为单词“optional”（可选）看起来会暗示该值是可选的，而它真正的含义是“它可以是 `None`”，即使它并不是可选的，仍然是必填的。

我认为 `Union[SomeType, None]` 更能明确表达其含义。

这只是关于词语和命名的问题，但这些词语会影响你和你的队友如何看待代码。

举个例子，看这段函数：

```python
from typing import Optional


def say_hi(name: Optional[str]):
    print(f"Hey {name}!")
```

参数 `name` 被定义为 `Optional[str]`，但它并不是“可选”的，你不能不传这个参数就调用函数：

```Python