HashMap和ConcurrentHashMap的并发性能测试

先看看代码吧，模拟1000个并发，每个测试1000次操作，循环测试10轮。分别测试Put和Get操作?

1. import?java.util.Collections;
2. import?java.util.HashMap;
3. import?java.util.Hashtable;
4. import?java.util.Map;
5. import?java.util.concurrent.ConcurrentHashMap;
6. public?class?T?{
7. ??static?final?int?threads?=?1000;
8. ??static?final?int?NUMBER?=?1000;
9. ??public?static?void?main(String[]?args)?throws?Exception?{
10. ????Map<String,?Integer>?hashmapSync?=?Collections
11. ????????.synchronizedMap(new?HashMap<String,?Integer>());//同步的hashmap
12. ????Map<String,?Integer>?concurrentHashMap?=?new?ConcurrentHashMap<String,?Integer>();
13. ????Map<String,?Integer>?hashtable?=?new?Hashtable<String,?Integer>();
14. ????long?totalA?=?0;
15. ????long?totalB?=?0;
16. ????long?totalC?=?0;
17. ????for?(int?i?=?0;?i?<=?10;?i++)?{
18. ??????totalA?+=?testPut(hashmapSync);
19. ??????totalB?+=?testPut(concurrentHashMap);
20. ??????totalC?+=?testPut(hashtable);
21. ????}
22. ????System.out.println("Put?time?HashMapSync="?+?totalA?+?"ms.");
23. ????System.out.println("Put?time?ConcurrentHashMap="?+?totalB?+?"ms.");
24. ????System.out.println("Put?time?Hashtable="?+?totalC?+?"ms.");
25. ????totalA?=?0;
26. ????totalB?=?0;
27. ????totalC?=?0;
28. ????for?(int?i?=?0;?i?<=?10;?i++)?{
29. ??????totalA?+=?testGet(hashmapSync);
30. ??????totalB?+=?testGet(concurrentHashMap);
31. ??????totalC?+=?testGet(hashtable);
32. ????}
33. ????System.out.println("Get?time?HashMapSync="?+?totalA?+?"ms.");
34. ????System.out.println("Get?time?ConcurrentHashMap="?+?totalB?+?"ms.");
35. ????System.out.println("Get?time?Hashtable="?+?totalC?+?"ms.");
36. ??}
37. ??public?static?long?testPut(Map<String,?Integer>?map)?throws?Exception?{
38. ????long?start?=?System.currentTimeMillis();
39. ????for?(int?i?=?0;?i?<?threads;?i++)?{
40. ??????new?MapPutThread(map).start();
41. ????}
42. ????while?(MapPutThread.counter?>?0)?{
43. ??????Thread.sleep(1);
44. ????}
45. ????return?System.currentTimeMillis()?-?start;
46. ??}
47. ??public?static?long?testGet(Map<String,?Integer>?map)?throws?Exception?{
48. ????long?start?=?System.currentTimeMillis();
49. ????for?(int?i?=?0;?i?<?threads;?i++)?{
50. ??????new?MapPutThread(map).start();
51. ????}
52. ????while?(MapPutThread.counter?>?0)?{
53. ??????Thread.sleep(1);
54. ????}
55. ????return?System.currentTimeMillis()?-?start;
56. ??}
57. }
58. class?MapPutThread?extends?Thread?{
59. ??static?int?counter?=?0;
60. ??static?Object?lock?=?new?Object();
61. ??private?Map<String,?Integer>?map;
62. ??private?String?key?=?this.getId()?+?"";
63. ??MapPutThread(Map<String,?Integer>?map)?{
64. ????synchronized?(lock)?{
65. ??????counter++;
66. ????}
67. ????this.map?=?map;
68. ??}
69. ??public?void?run()?{
70. ????for?(int?i?=?1;?i?<=?T.NUMBER;?i++)?{
71. ??????map.put(key,?i);
72. ????}
73. ????synchronized?(lock)?{
74. ??????counter--;
75. ????}
76. ??}
77. }
78. class?MapGetThread?extends?Thread?{
79. ??static?int?counter?=?0;
80. ??static?Object?lock?=?new?Object();
81. ??private?Map<String,?Integer>?map;
82. ??private?String?key?=?this.getId()?+?"";
83. ??MapGetThread(Map<String,?Integer>?map)?{
84. ????synchronized?(lock)?{
85. ??????counter++;
86. ????}
87. ????this.map?=?map;
88. ??}
89. ??public?void?run()?{
90. ????for?(int?i?=?1;?i?<=?T.NUMBER;?i++)?{
91. ??????map.get(key);
92. ????}
93. ????synchronized?(lock)?{
94. ??????counter--;
95. ????}
96. ??}
97. }

运行结果：
Put time HashMapSync=3966ms.
Put time ConcurrentHashMap=1892ms.
Put time Hashtable=3892ms.
Get time HashMapSync=3812ms.
Get time ConcurrentHashMap=1828ms.
Get time Hashtable=3985ms.


结论：?
ConcurrentHashMap的性能比同步的HashMap快一倍左右?
同步的HashMap和Hashtable的性能相当?

转自：http://blog.csdn.net/java2000_net/archive/2008/11/25/3373181.aspx