Java Package Structure--Some Thought

why do we need package in java?
in irder to better originize classes, java provide package. package will be put the similiar interface or classes in the same package. besides, different package can contains the classes with the same name. thats why when we import classes with same name from different classes, the import statement should shtart with package name.

common pacage in java:
java.lang. (basic classes)
java.io. (classes that contains input and output methods)
java.util. (container)

some commonly used data structures:
java.util:
Interfaces:

1. Collection
2. Comparator
3. Iterator
4. ListIterator
5. Enumeration
6. Deque
7. Queue
8. Map<K, V>
9. Map.Entry<K, V>
10. SortedMap<K, V>
11. SortedSet
12. Set
13. EventListener
    Classes:
14. ArrayList
15. Arrays
16. BitSet
17. Collections
18. Dictionary<K, V>
19. HashSet / LinkedHashSet
20. HashMap<K, V> / LinkedHashMap<K, V>
21. LinkedList
22. PriorityQueue
23. Random
24. Scanner
25. Stack
26. TreeMap<K, V>
27. TreeSet

Java.lang package
28. Boolean
29. Byte
30. Character
31. Double
32. Float
33. Integer
34. Long
35. Math
36. Object
37. Short
38. String
39. StringBuffer
40. StringBuilder
41. System
42. Thread