单例-枚举模式

常规的单例模式有以下几处缺点:

1.无法防止被反射,有人可能说加入flag变量控制,那么我在反射的时候提前修改flag,不就可以了么?
2.无法防止被序列化创建.
那么我们可以采用枚举的方式来优化.

public class SingleInstance {

   public static void main(String[] args) throws Exception {
       Single instance = Single.Instance;
       System.out.println(instance.getAge() + "");
       //枚举抗序列化
               Single deepClone = deepClone(instance);
               int age = deepClone.getAge();
               System.out.println(instance==deepClone);
       //枚举抗反射
       Class<Single> clazz = Single.class;
       Constructor<Single> constructor = clazz.getConstructor(null);
       constructor.setAccessible(true);
       Single single = constructor.newInstance(null);
       
       
       
       
   }
   
   public static <T> T deepClone(T src) {
       ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
       ObjectOutputStream out = null;
       try {
           out = new ObjectOutputStream(byteOut);
           out.writeObject(src);
           ByteArrayInputStream byteIn = new ByteArrayInputStream(byteOut.toByteArray());
           ObjectInputStream in = new ObjectInputStream(byteIn);
           T dest = (T) in.readObject();
           return dest;
       } catch (IOException e) {
           e.printStackTrace();
       } catch (ClassNotFoundException e) {
           e.printStackTrace();
       }
       return null;
   }

}



enum Single {
   Instance(10);

   private int age;

   private Single(int num) {
       age = num;
   }

   public int getAge() {
       return age;
   }
}

测试结果:

image.png