java 各个版本的对应关系
| JDK版本号 | Class版本号 | 16进制 |
| 1.1 | 45.0 | 00 00 00 2D |
| 1.2 | 46.0 | 00 00 00 2E |
| 1.3 | 47.0 | 00 00 00 2F |
| 1.4 | 48.0 | 00 00 00 30 |
| 1.5 | 49.0 | 00 00 00 31 |
| 1.6 | 50.0 | 00 00 00 32 |
| 1.7 | 51.0 | 00 00 00 33 |
| 1.8 | 52.0 | 00 00 00 34 |
| 9 | 53.0 | 00 00 00 35 |
| 10 | 54.0 | 00 00 00 36 |
| 11 | 55.0 | 00 00 00 37 |
| 12 | 56.0 | 00 00 00 38 |
| 13 | 57.0 | 00 00 00 39 |
| 14 | 58.0 | 00 00 00 3a |
| 15 | 59.0 | 00 00 00 3b |
| 16 | 60.0 | 00 00 00 3c |
| 17 | 61.0 | 00 00 00 3d |
| 18 | 62.0 | 00 00 00 3e |
