What is singleton class and its implementation?

In object-oriented programming, a singleton class is a class that can have only one object (an instance of the class) at a time. After first time, if we try to instantiate the Singleton class, the new variable also points to the first instance created.

What are the different ways to implement Singleton pattern?

Here is the UML diagram of Singleton design pattern in Java and then we’ll see how you can implement Singleton pattern in Java:

Lazy initialization, non-thread-safe:
Non-lazy initialization, thread-safe.
Lazy initialization, thread-safe.
Double-check locking.
Nested initialization.

How does Singleton pattern work?

The Singleton pattern disables all other means of creating objects of a class except for the special creation method. This method either creates a new object or returns an existing one if it has already been created. Use the Singleton pattern when you need stricter control over global variables.

How does Singleton work in Java?

A Singleton class in Java allows only one instance to be created and provides global access to all other classes through this single object or instance. Similar to the static fields, The instance fields(if any) of a class will occur only for a single time.

Where is singleton pattern used?

It is used where only a single instance of a class is required to control the action throughout the execution. A singleton class shouldn’t have multiple instances in any case and at any cost. Singleton classes are used for logging, driver objects, caching and thread pool, database connections.

Where is Singleton pattern used?

How can singleton be broken?

Serialization is used to convert an object of byte stream and save in a file or send over a network. Suppose you serialize an object of a singleton class. Then if you de-serialize that object it will create a new instance and hence break the singleton pattern.

What is the benefit of singleton pattern?

Instance control: Singleton prevents other objects from instantiating their own copies of the Singleton object, ensuring that all objects access the single instance. Flexibility: Since the class controls the instantiation process, the class has the flexibility to change the instantiation process.

What is the benefit of Singleton pattern?

Why can’t we use static class instead of Singleton?

Static class objects cannot be passed as parameters to other methods whereas we can pass instances of a singleton as a parameter to another method. For example we can modify our normal class to have a method which takes a singleton class instance as a parameter. We cannot do this with static classes.

What are the uses of Singleton patterns in Java?

Singleton pattern restricts the instantiation of a class and ensures that only one instance of the class exists in the java virtual machine.

The singleton class must provide a global access point to get the instance of the class.

caching and thread pool.

How to create a singleton in Java?

Method 1 – Lazy initialization. The lazy initialization will create the singleton object only if is necessary.

then the object can be created at

Method 3 – Static block initialization.

Method 4 – Using enum.

When to use Singleton?

A singleton should be used when managing access to a resource which is shared by the entire application, and it would be destructive to potentially have multiple instances of the same class. Making sure that access to shared resources thread safe is one very good example of where this kind of pattern can be vital.

What does Singleton mean in Java?

A singleton in Java is a class for which only one instance can be created. It provides a global point of access this instance. The singleton pattern describe how this can be archived.