volatile

1. 一般的，如果多个线程协作存、取某个变量时，一般需要用到synchronized关键字进行同步操作，如：
2. publicclassMyTestThreadextendsMyTestimplementsRunnable{
3. privateboolean_done=false;
4. publicsynchronizedbooleangetDone()
5. {
6. return_done;
7. }
8. publicsynchronizedvoidsetDone(booleanb)
9. {
10. _done=b;
11. }
13. publicvoidrun(){
14. booleandone;
15. done=getDone();
16. while(!done){
17. repaint();
18. try{
19. Thread.sleep(100);
20. }catch(InterruptedExceptionie){
21. return;
22. }
23. }
24. }
25. }
26. 或者：
27. publicclassMyTestThreadextendsMyTestimplementsRunnable{
28. privateboolean_done=false;
29. publicvoidsetDone(booleanb)
30. {
31. synchronized(this)
32. {
33. _done=b;
34. }
35. }
37. publicvoidrun(){
38. booleandone;
39. synchronized(this)
40. {
41. done=_done;
42. }
44. while(!done){
45. repaint();
46. try{
47. Thread.sleep(100);
48. }catch(InterruptedExceptionie){
49. return;
50. }
51. }
52. }
53. }
54. 但是，通过volatile关键字，我们可以大大简化：
55. publicclassMyTestThreadextendsMyTestimplementsRunnable{
56. privatevolatilebooleandone=false;
57. publicvoidrun(){
58. while(!done){
59. repaint();
60. try{
61. Thread.sleep(100);
62. }catch(InterruptedExceptionie){
63. return;
64. }
65. }
66. }
67. publicvoidsetDone(booleanb){
68. done=b;
69. }
70. }