1. /**
  2. * 一种错误的单例写法，线程不安全
  3. */
  4. private static Singleton uniqueSingleton;
  5. private Singleton() {
  6. }
  7. public static Singleton getInstance() {
  8. if (uniqueSingleton == null) {
  9. uniqueSingleton = new Singleton();
  10. }
  11. return uniqueSingleton;
  12. }
  1. /**
  2. * 线程安全的懒加载，影响效率，JVM不保证执行顺序
  3. */
  4. private static Singleton uniqueSingleton;
  6. private Singleton() {
  8. }
  10. public static synchronized Singleton getInstance() {
  11. if (uniqueSingleton == null) {
  12. uniqueSingleton = new Singleton();
  13. }
  15. return uniqueSingleton;
  16. }
  18. /**
  19. * 急加载模式,线程安全，代码简单
  20. */
  21. private final static Singleton singleton = new Singleton();
  23. private Singleton() {
  25. }
  27. public static Singleton getInstance() {
  28. return singleton;
  29. }
  31. /**
  32. * 懒加载，双重锁保证，线程安全
  33. */
  34. private static volatile Singleton singleton;
  36. private Singleton() {
  37. }
  39. private static Singleton getInstance() {
  40. if (singleton == null) {
  41. synchronized (Singleton.class) {
  42. if (singleton == null) {
  43. return new Singleton();
  44. }
  45. }
  46. }
  47. return singleton;
  48. }
  50. /**
  51. * 懒加载的内部类写法，线程安全，懒加载
  52. */
  53. private static class SingletonHolder {
  54. private final static Singleton singleton = new Singleton();
  55. }
  57. private Singleton() {
  58. }
  60. public static Singleton getInstance() {
  61. return SingletonHolder.singleton;
  62. }

版权声明：本文为batmand原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。
本文链接：https://www.cnblogs.com/batmand/p/8552920.html