# WithKeys.java

    package org.thewonderlemming.c4plantuml.graphml.model;

    import java.util.Collections;
    import java.util.List;
    import java.util.function.Function;

    /**
     * A basic Java {@link Function} to create fluent builders such as {@link GraphMLModel#builder()}.
     *
     * @author thewonderlemming
     *
     * @param <T> the type of the result of the function.
     */
    @FunctionalInterface
    public interface WithKeys<T> {

        /**
         * Takes a list of {@link KeyModel}, processes it and returns a results of type T.
         *
         * @param keys the parameter given to the function.
         * @return the results of the function.
         */
        T withKeys(final List<KeyModel> keys);

        /**
         * A semantic call to pass no value to the current function.
         *
         * @return the results of the function.
         */
        default T withoutKeys() {
            return withKeys(Collections.emptyList());
        }
    }