[logseq-plugin-git:commit] 2024-07-01T05:24:58.263Z

journals/2024_07_01.md

@@ -14,7 +14,44 @@
 	- 调用的时间是不确定的
 - 手写单例模式 #card #java
   id:: 66820808-c5d5-4c44-a5f3-f6273725469d
-	-
+	- 饿汉式
+	- ```java
+	  public class Singleton {
+	  	private static Singleton instance = new Singleton()
+	  	private Singleton() {}
+	  	public static Singlton getSingleton() {
+	        	return instance;
+	      }
+	  }
+	  ```
+	- 懒汉式
+	- ```java
+	  public class Singleton {
+	  	private static Singleton singleton;
+	  	private Singleton() {}
+	  	public synchronized static Singlton getSingleton() {
+	      	if (singleton == null) {	
+	            singleton = new Singleton();
+	          }
+	      	return singleton;
+	      }
+	  }
+	  
+	  public class Singleton {
+	  	private volatile static Singleton singleton;
+	  	private Singleton() {}
+	  	public static Singlton getSingleton() {
+	      	if (singleton == null) {
+	          	synchronized (Singlton.class) {
+	              	if (singleton == null) {
+	                  	singleton = new Singleton();
+	                  }
+	              }
+	          }
+	      	return singleton;
+	      }
+	  }
+	  ```
 - 用了redis哪些数据结构 #card #java
   id:: 66820850-48cc-4bde-8ec6-8ca8ce5d42e0
 	- string，存验证码，缓存常用的一些数据