## 高并發下線程安全的單例模式 #### Double Check Locking 雙檢查鎖機制 ``` public class MySingleton { //使用volatile關鍵字保其可見性 volatile private static MySingleton instance = null; private MySingleton(){} public static MySingleton getInstance() { try { if(instance != null){//懶漢式 }else{ //創建實例之前可能會有一些準備性的耗時工作 Thread.sleep(300); synchronized (MySingleton.class) { if(instance == null){//二次檢查 instance = new MySingleton(); } } } } catch (InterruptedException e) { e.printStackTrace(); } return instance; } } ``` #### 使用靜態內置類實現單例模式 ``` public class MySingleton { //內部類 private static class MySingletonHandler{ private static MySingleton instance = new MySingleton(); } private MySingleton(){} public static MySingleton getInstance() { return MySingletonHandler.instance; } } ``` #### 使用static代碼塊實現單例 ``` public class MySingleton{ private static MySingleton instance = null; private MySingleton(){} static{ instance = new MySingleton(); } public static MySingleton getInstance() { return instance; } } ``` 更多方法：[https://blog.csdn.net/cselmu9/article/details/51366946](https://blog.csdn.net/cselmu9/article/details/51366946/)