Update Singleton.java

Singleton can be broken using serialization and reflection. We have to protect our class for that. Check this:
https://codippa.com/how-to-break-singleton-in-java/

Author: Piyush-Blackbuck-121

src/create/singleton/Singleton.java

@@ -8,7 +8,10 @@
 public class Singleton {
     //防止外部创建实例
     private Singleton() {
-
+        //To save singleton from reflection
+        if(mInstance != null) {
+            throw new InstantiationError("Already there");
+        }
     }
     //唯一实例
     private static volatile Singleton mInstance;
@@ -25,4 +28,9 @@ public static Singleton getInstance() {
         }
         return mInstance;
     }
+    
+     //To save singleton from Deserialization
+    protected Object readResolve() {
+        return mInstance;
+    }
 }