Method fromProperties

guava/src/com/google/common/collect/Maps.java:1401–1438

Creates an {@code ImmutableMap<String, String>} from a {@code Properties} instance. Properties normally derive from {@code Map<Object, Object>}, but they typically contain strings, which is awkward. This method lets you get a plain-old-{@code Map} out of a {@code Properties}. @param properties a {@

(Properties properties)

   * @throws NullPointerException if any key or value in {@code properties} is null
   */
  @J2ktIncompatible
  @GwtIncompatible // java.util.Properties
  public static ImmutableMap<String, String> fromProperties(Properties properties) {
    ImmutableMap.Builder<String, String> builder = ImmutableMap.builder();

    for (Enumeration<?> e = properties.propertyNames(); e.hasMoreElements(); ) {
      /*
       * requireNonNull is safe because propertyNames contains only non-null elements.
       *
       * Accordingly, we have it annotated as returning `Enumeration<? extends Object>` in our
       * prototype checker's JDK. However, the checker still sees the return type as plain
       * `Enumeration<?>`, probably because of one of the following two bugs (and maybe those two
       * bugs are themselves just symptoms of the same underlying problem):
       *
       * https://github.com/typetools/checker-framework/issues/3030
       *
       * https://github.com/typetools/checker-framework/issues/3236
       */
      String key = (String) requireNonNull(e.nextElement());
      /*
       * requireNonNull is safe because the key came from propertyNames...
       *
       * ...except that it's possible for users to insert a string key with a non-string value, and
       * in that case, getProperty *will* return null.
       *
       * TODO(b/192002623): Handle that case: Either:
       *
       * - Skip non-string keys and values entirely, as proposed in the linked bug.
       *
       * - Throw ClassCastException instead of NullPointerException, as documented in the current
       *   Javadoc. (Note that we can't necessarily "just" change our call to `getProperty` to `get`
       *   because `get` does not consult the default properties.)
       */
      builder.put(key, requireNonNull(properties.getProperty(key)));
    }

    return builder.buildOrThrow();
  }

  /**
   * Returns an immutable map entry with the specified key and value. The {@link Entry#setValue}