Is task execution unordered?

Here’s two ways that I know of to add project dependencies.

void addProjectDeps(Project project, Configuration config) {
   Project p1 = project.project(':project1');
   Project p2 = project.project(':project2');
   DependencyHandler dh = project.getDependencies();
   dh.add(config.getName(), p1); // only works when project.configurations.contains(config) 
   Dependency d2 = dh.create(p2);
   config.getDependencies().add(p2);
}