Singleton design patterns in java pdf

And also in static block, we can handle the exceptions. It also creates class instance whether it is required or not by the user like in Eager initialization. But in this also, the problem of resource wastage still occurs as it also creates class instance whether it is required or not. This overcomes the drawback of both eager and static block initialization as it first checks if class instance is required or not and then allows to create the instance. It first checks if the instance is null or not.

If null then it allows us to create an instance and return its reference else return the previously created instance reference. Whenever we de-serialize a class, it creates a new instance of the class. This can be challenging, especially with Singleton pattern. This causes issue as we are getting a new instance and defeating the purpose of the Singleton.

We can handle this by implementing the readResolve. In this article, we look at the Singleton Design Pattern with its use cases. We covered some of the benefit and drawbacks of using this design pattern. In the last part, we talked about when to use this design pattern in the real-life scenario.

This site uses Akismet to reduce spam. Learn how your comment data is processed. Singleton Design Pattern ensures that there is only one instance for this class.

This is very useful with shared resources. Java also have an object called ThreadLocal , which creates a single instance of an object on a thread by thread basis. This could be useful in applications where each thread need its own version of the object. Here is also a Singleton implementation with enum containing only one element :.

To create the singleton class, we need to have static member of class, private constructor and static factory method. In such case, we create the instance of the class at the time of declaring the static data member, so instance of the class is created at the time of classloading.

In such case, we create the instance of the class in synchronized method or synchronized block, so instance of the class is created when required.

If singleton class is Serializable, you can serialize the singleton instance. Once it is serialized, you can deserialize it but it will not return the singleton object. To resolve this issue, you need to override the readResolve method that enforces the singleton. It is called just after the object is deserialized.

It returns the singleton object. Assumption: you have created a table userdata that has three fields uid, uname and upassword in mysql database. Database name is ashwinirajput, username is root, password is ashwini.

JavaTpoint offers too many high quality services. Mail us on [email protected] , to get more information about given services. Please mail your requirement at [email protected] Duration: 1 week to 2 week. Design Patterns. BufferedReader; import java. IOException; import java. InputStreamReader; import java. Connection; import java. DriverManager; import java.