### Question:
PrefetchTreeNode implements Serializable, XMLSerializable { public PrefetchTreeNode addPath(String path) { if (Util.isEmptyString(path)) { throw new IllegalArgumentException("Empty path: " + path); } PrefetchTreeNode node = this; StringTokenizer toks = new StringTokenizer(path, Entity.PATH_SEPARATOR); while (toks.hasMoreTokens()) { String segment = toks.nextToken(); PrefetchTreeNode child = node.getChild(segment); if (child == null) { child = new PrefetchTreeNode(node, segment); node.addChild(child); } node = child; } return node; } PrefetchTreeNode(); protected  PrefetchTreeNode(PrefetchTreeNode parent, String name); static PrefetchTreeNode withPath(String path, int semantics); @Override void encodeAsXML(XMLEncoder encoder, ConfigurationNodeVisitor delegate); PrefetchTreeNode getRoot(); String getPath(); String getPath(PrefetchTreeNode upTillParent); Collection<PrefetchTreeNode> adjacentJointNodes(); Collection<PrefetchTreeNode> jointNodes(); Collection<PrefetchTreeNode> disjointNodes(); Collection<PrefetchTreeNode> disjointByIdNodes(); Collection<PrefetchTreeNode> nonPhantomNodes(); PrefetchTreeNode cloneJointSubtree(); void traverse(PrefetchProcessor processor); PrefetchTreeNode getNode(String path); PrefetchTreeNode addPath(String path); void merge(PrefetchTreeNode node); void removePath(String path); void addChild(PrefetchTreeNode child); void removeChild(PrefetchTreeNode child); PrefetchTreeNode getParent(); Collection<PrefetchTreeNode> getChildren(); boolean hasChildren(); String getName(); boolean isPhantom(); void setPhantom(boolean phantom); int getSemantics(); void setSemantics(int semantics); boolean isJointPrefetch(); boolean isDisjointPrefetch(); boolean isDisjointByIdPrefetch(); String getEjbqlPathEntityId(); void setEjbqlPathEntityId(String ejbqlPathEntityId); String getEntityName(); void setEntityName(String entityName); static final int UNDEFINED_SEMANTICS; static final int JOINT_PREFETCH_SEMANTICS; static final int DISJOINT_PREFETCH_SEMANTICS; static final int DISJOINT_BY_ID_PREFETCH_SEMANTICS; }### Answer:
@Test public void testAddPath() { PrefetchTreeNode tree = new PrefetchTreeNode(); tree.addPath("abc"); tree.addPath("abc.def.mnk"); tree.addPath("xyz"); assertTrue(tree.isPhantom()); PrefetchTreeNode n1 = tree.getNode("abc"); assertNotNull(n1); assertTrue(n1.isPhantom()); assertEquals("abc", n1.getName()); PrefetchTreeNode n2 = tree.getNode("abc.def"); assertNotNull(n2); assertTrue(n2.isPhantom()); assertEquals("def", n2.getName()); PrefetchTreeNode n3 = tree.getNode("abc.def.mnk"); assertNotNull(n3); assertTrue(n3.isPhantom()); assertEquals("mnk", n3.getName()); PrefetchTreeNode n4 = tree.getNode("xyz"); assertNotNull(n4); assertTrue(n4.isPhantom()); assertEquals("xyz", n4.getName()); }