assertBothExistsAndOneIsBeforeOther(hierarchy, middle1, root1);
        assertBothExistsAndOneIsBeforeOther(hierarchy, middle2, root2);
    }

    private static void assertBothExistsAndOneIsBeforeOther(Set<Configuration> hierarchy, Configuration beforeConf, Configuration afterConf) {
        assert hierarchy.contains(beforeConf)
        assert hierarchy.contains(afterConf)

 * #getRepositories()} method to manage the repositories.</p>
 *
 * <h3>Multi-project Builds</h3>
 *
 * <p>Projects are arranged into a hierarchy of projects. A project has a name, and a fully qualified path which
 * uniquely identifies it in the hierarchy.</p>
 *
 * <h3>Plugins</h3>
 *
 * <p>
 * Plugins can be used to modularise and reuse project configuration.

* **Roles**: Configuration roles should be set upon creation and not changed afterward.
* **Hierarchy**: Configuration hierarchy (`extendsFrom`) should be set upon creation. Mutating the hierarchy prior to resolution is highly discouraged, but is permitted within a `withDependencies` hook.

        validateMutation(MutationType.HIERARCHY);
        for (Configuration configuration : extendsFrom) {
            if (configuration.getHierarchy().contains(this)) {
                throw new InvalidUserDataException(String.format(
                    "Cyclic extendsFrom from %s and %s is not allowed. See existing hierarchy: %s", this,
                    configuration, configuration.getHierarchy()));

 *
 * <p>Service registries are arranged in a hierarchy. If a service of a given type cannot be located, the registry uses its parent registry, if any, to locate the service.</p>
 *

     *
     * @return The parent directory of this SMB resource or
     *         <code>smb://</code> if the resource refers to the root of the URL
     *         hierarchy which incidentally is also <code>smb://</code>.
     */
    public String getParent () {
        return this.fileLocator.getParent();
    }


    /**

//	mcentral: collects all spans of a given size class.
//	mcache: a per-P cache of mspans with free space.
//	mstats: allocation statistics.
//
// Allocating a small object proceeds up a hierarchy of caches:
//
//	1. Round the size up to one of the small size classes
//	   and look in the corresponding mspan in this P's mcache.
//	   Scan the mspan's free bitmap to find a free slot.

In other words, you can use a file tree wherever a file collection is required, but remember that a file collection is a flat list/set of files, while a file tree is a file and directory hierarchy.
To convert a file tree to a flat collection, use the link:{javadocPath}/org/gradle/api/file/FileTree.html#getFiles--[FileTree.getFiles()] property.