The code should use the public static final fields that define the constnat value of default value, instead of value being hardcoded.
Example: https://github.com/undertow-io/undertow/blob/master/core/src/main/java/io/undertow/server/handlers/form/FormEncodedDataDefinition.java#L111 - direct input, rather than dependency on default value defined in https://github.com/undertow-io/undertow/blob/master/core/src/main/java/io/undertow/UndertowOptions.java#L84

this.data = new FormData(exchange.getConnection().getUndertowOptions().get(UndertowOptions.MAX_PARAMETERS, 1000));

It should be using the value defined in https://github.com/undertow-io/undertow/blob/main/core/src/main/java/io/undertow/UndertowOptions.java#L84 instead:

public static final int DEFAULT_MAX_PARAMETERS = 1000;

Also, the Javadoc in UndertowOptions needs fixing, it has the numeric value, rather than proper link with @link