请问java中哪一个类可以很方便的处理“树”这个数据结构？

可以参考jdk中的TreeModel接口，可以单独拿出来对树结构进行操作。
实例可以在网上搜索一下JTree的用法。

java.util
接口 Collection
所有超级接口：
Iterable
所有已知子接口：
BeanContext, BeanContextServices, BlockingDeque, BlockingQueue, Deque, List, NavigableSet, Queue, Set, SortedSet
所有已知实现类：
AbstractCollection, AbstractList, AbstractQueue, AbstractSequentialList, AbstractSet, ArrayBlockingQueue, ArrayDeque, ArrayList, AttributeList, BeanContextServicesSupport, BeanContextSupport, ConcurrentLinkedQueue, ConcurrentSkipListSet, CopyOnWriteArrayList, CopyOnWriteArraySet, DelayQueue, EnumSet, HashSet, JobStateReasons, LinkedBlockingDeque, LinkedBlockingQueue, LinkedHashSet, LinkedList, PriorityBlockingQueue, PriorityQueue, RoleList, RoleUnresolvedList, Stack, SynchronousQueue, TreeSet, Vector