Jgit traverse content of a commit from specific branch

How can I traverse with jgit all content of an specific commit from an specific branch?

ObjectId commitId = repository.resolve(currentCommit.getCommitHash());
RevWalk revWalk = new RevWalk(repository);
RevCommit commit = revWalk.parseCommit(commitId);
RevTree tree = commit.getTree();
TreeWalk treeWalk = new TreeWalk(repository);
if (!treeWalk.next()) {
    throw new IllegalStateException(
            "Did not find expected file README.md");

This code retrieve me a special file from the commit but I want traverse all content of an commit.

Git Baby is a git and github fan, let's start git clone.