protected void appendContents(TreeFormatter formatter) {
                formatter.node("filtered collection");
                formatter.startChildren();
                CompositeFileCollection.this.describeContents(formatter);
                formatter.endChildren();
            }

            @Override
            public String getDisplayName() {
                return CompositeFileCollection.this.getDisplayName();

     * @return the display name
     */
    String getDisplayName();

    /**
     * Appends diagnostic information about the contents of this collection to the given formatter.
     */
    TreeFormatter describeContents(TreeFormatter formatter);

    /**
     * Calculates the execution time value of this file collection. The resulting value is serialized to the configuration cache

        return tree.getDisplayName();
    }

    @Override
    protected void appendContents(TreeFormatter formatter) {
        formatter.node("backing tree");
        formatter.startChildren();
        tree.describeContents(formatter);
        formatter.endChildren();
    }

    public FileTreeInternal getTree() {
        return tree;
    }

    /**

    @Override
    protected void appendContents(TreeFormatter formatter) {
        formatter.node("source");
        formatter.startChildren();
        for (FileCollectionInternal files : source) {
            files.describeContents(formatter);
        }
        formatter.endChildren();
    }

    public Set<? extends FileCollection> getSources() {
        return source;
    }

    @Override

     */
    protected abstract String describeContents();

    // This method is final - implement describeContents() instead
    @Override
    protected final String toStringNoReentrance() {
        if (displayName != null) {
            return displayName.toString();
        } else {
            return describeContents();
        }
    }

    @Override

        formatter.node("source set: " + outputDirectories.toString());
        formatter.node("output directories");
        formatter.startChildren();
        ((FileCollectionInternal) outputDirectories).describeContents(formatter);
        formatter.endChildren();
    }

    @Override
    public ConfigurableFileCollection getClassesDirs() {
        return classesDirs;
    }

    /**

    }

    @Override
    protected void appendContents(TreeFormatter formatter) {
        formatter.node("backing collection");
        formatter.startChildren();
        collection.describeContents(formatter);
        formatter.endChildren();
    }

    public AbstractFileCollection getCollection() {
        return collection;
    }

    @Override

    }

    @Override
    protected boolean isDefaultConvention() {
        return getConventionSupplier() == NOT_DEFINED;
    }

    @Override
    protected String describeContents() {
        // NOTE: Do not realize the value of the Provider in toString().  The debugger will try to call this method and make debugging really frustrating.

        return getDisplayName();
    }

    /**
     * This is final - override {@link #appendContents(TreeFormatter)}  instead to add type specific content.
     */
    @Override
    public final TreeFormatter describeContents(TreeFormatter formatter) {
        formatter.node("collection type: ").appendType(getClass()).append(" (id: ").append(String.valueOf(System.identityHashCode(this))).append(")");
        formatter.startChildren();

        }

        private void appendItem(TreeFormatter formatter, Object item) {
            if (item instanceof FileCollectionInternal) {
                ((FileCollectionInternal) item).describeContents(formatter);
            } else if (item instanceof ArrayList) {
                for (Object child : (List) item) {
                    appendItem(formatter, child);
                }
            } else {