What is a singleton class and when do you use it?

Asked by Last Modified  

10 Answers

Learn Java

Follow 3
Answer

Please enter your answer

Vishal Deep

11+ year of IT Experience in Manual & Automation(Java + Selenium+Rest Assured) Testing

Singleton class have a private constructor. while we can't create an object from outside of class, we can create an object only once.
Comments
Dislike Bookmark

2 Days Free Demo Classes

One reason that tends to come up over and over again on the internets is that of a "logging" class (which you mentioned). In this case, a Singleton can be used instead of a single instance of a class because a logging class usually needs to be used over and over again ad nauseam by every class in a project....
read more
One reason that tends to come up over and over again on the internets is that of a "logging" class (which you mentioned). In this case, a Singleton can be used instead of a single instance of a class because a logging class usually needs to be used over and over again ad nauseam by every class in a project. If every class uses this logging class, dependency injection becomes cumbersome. Logging is a specific example of an "acceptable" Singleton because it doesn't affect the execution of your code. Disable logging, code execution remains the same. Enable it, same same. Misko puts it in the following way in Root Cause of Singletons, "The information here flows one way: From your application into the logger. Even though loggers are global state, since no information flows from loggers into your application, loggers are acceptable." read less
Comments
Dislike Bookmark

Tutor

Singleton class has only one instance and is generally meant for shortened finish of a program
Comments
Dislike Bookmark

Big Data Expert

A class is called singleton when it limits the number of object creation for that class to be one. We can't have more than a single object of that class. Singleton class are employed extensively in concepts like networking and database connectivity.
Comments
Dislike Bookmark

Trainer

singleton is a design pattern that restricts the instantiation of a class to one object.
Comments
Dislike Bookmark

B.E. (IT)

One reason that tends to come up over and over again on the internets is that of a "logging" class (which you mentioned). In this case, a Singleton can be used instead of a single instance of a class because a logging class usually needs to be used over and over again ad nauseam by every class in a project....
read more
One reason that tends to come up over and over again on the internets is that of a "logging" class (which you mentioned). In this case, a Singleton can be used instead of a single instance of a class because a logging class usually needs to be used over and over again ad nauseam by every class in a project. If every class uses this logging class, dependency injection becomes cumbersome. Logging is a specific example of an "acceptable" Singleton because it doesn't affect the execution of your code. Disable logging, code execution remains the same. Enable it, same same. Misko puts it in the following way in Root Cause of Singletons, "The information here flows one way: From your application into the logger. Even though loggers are global state, since no information flows from loggers into your application, loggers are acceptable." Singleton candidate must satisfy three requirements: controls concurrent access to a shared resource. access to the resource will be requested from multiple, disparate parts of the system. there can be only one object. If your proposed Singleton has only one or two of these requirements, a redesign is almost always the correct option. For example, a printer spooler is unlikely to be called from more than one place (the Print menu), so you can use mutexes to solve the concurrent access problem. A simple logger is the most obvious example of a possibly-valid Singleton, but this can change with more complex logging schemes. read less
Comments
Dislike Bookmark

Java trainer , Data structure and algorithms

Singleton design pattern can be obtained by using following steps: 1.Private Constructor 2.Static Factory Method 3.Static Reference Object Creation As we are using a Static Reference Object Creation ,it is a "static" member and a static member can execute only one time and will create only one object. Creating...
read more
Singleton design pattern can be obtained by using following steps: 1.Private Constructor 2.Static Factory Method 3.Static Reference Object Creation As we are using a Static Reference Object Creation ,it is a "static" member and a static member can execute only one time and will create only one object. Creating only one Object for the entire class saves the memory space and which helps to not to degrade the performance, which is most important. Since we are able to create exactly one instance for one class ,it is called as Singleton class read less
Comments
Dislike Bookmark

Talent with Professional Experience

Singleton class is a class which has one instance
Comments
Dislike Bookmark

Trainer

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
Comments
Dislike Bookmark

Trainer

A singleton class is one which has only one object of itself own which is a static object and outside the class we cant create another object as the constructor is private.
Comments
Dislike Bookmark

View 8 more Answers

Related Questions

Presently is swings and applets are important in java ?
When compared to swing, nowadays SWT is getting popular, where you can built a application like eclipse.
Mahender
Why Java is platform independent?
Once your java code compiled, compiled code(.class) can be executed on any os platform...if your question is HOW..it is interesting which deals with bytecode conversation
Sunita
What are the advanced features of EJB3.1?
1. Support for direct use of EJBs in the servlet container, including simplified packaging options. The current thought is to allow EJBs in the WEB-INF/classes directory while allowing ejb-jar.xml to reside...
Arunava Chatterjee
Do I need to import java.lang package any time? Why?
No, you don't need to import it at any time. As this is part of java.lang package is a part of \jdk1.6.0_11{this is the location f your jdk installation directory}\jre\lib\rt.jar and this rt.jar (called...
Anitha
Which is a good Java training and placement institute for a fresher in Bangalore?
I know an institute in HYderabad which is giving 100% job guarantee or 100% fee refund. They have office in bangalore also, not sure whether they are offering this program in Bangalore. Please visit their...
Raja
0 0
View Comments5

Now ask question in any of the 1000+ Categories, and get Answers from Tutors and Trainers on UrbanPro.com

Ask a Question

Related Lessons

Java inheritance example
Answer these questions Answer the above question

Kiran Kumar Matam

0 0
View Comments1
How To Setup development Environment Of Java?
After installation of JAVA, we need to setup 2 environment variables. First one is JAVA_HOME and second is Path. Below steps to set up Java environment to compile & execute Java programs from command...

Amit K.

0 0
View Comments0
jOOQ 3.10 Supports JPA Attribute Converter
One of the cooler hidden features in jOOQ is the JPADatabase, which allows for reverse engineering a pre-existing set of JPA-annotated entities to generate jOOQ code. For instance, you could write these...

Hasnain

3 0
View Comments0
Amazon written test for experience
For the below written test answer I defined with "*" at the end of the options NULL is the same as 0 for integer the same as blank for character * the same as 0 for integer and blank for character the...

Suresh

0 0
View Comments0
Inheritance In Java
Inheritance: The process of getting properties and behaviors from one class to another class is called inheritance. Properties: Variables Behaviors: Methods The main purpose of the inheritance...
D

Deleted U.

1 0
View Comments0

Recommended Articles

Why Java is the Most Popular Programming Language

Designed in a flexible and user-friendly demeanor, Java is the most commonly used programming language for the creation of web applications and platform. It allows developers to “write once, run anywhere” (WORA). It is general-purpose, a high-level programming language developed by Sun Microsystem. Initially known as an...

Read full article >

Some Popular IT Courses in Current Market

In the domain of Information Technology, there is always a lot to learn and implement. However, some technologies have a relatively higher demand than the rest of the others. So here are some popular IT courses for the present and upcoming future: Cloud Computing Cloud Computing is a computing technique which is used...

Read full article >

Why Should You Learn Java !

Java is the most famous programming language till date. 20 years is a big time for any programming language to survive and gain strength. Java has been proved to be one of the most reliable programming languages for networked computers. source:techcentral.com Java was developed to pertain over the Internet. Over...

Read full article >

Java: An Object-Oriented Language

Java is the most commonly used popular programming language for the creation of web applications and platform today. Integrated Cloud Applications and Platform Services Oracle says, “Java developers worldwide has over 9 million and runs approximately 3 billion mobile phones”.  Right from its first implication as java 1.0...

Read full article >

Find Java Certification near you
Java Certification in Bangalore
Java Certification in Hyderabad
Java Certification in Pune
Java Certification in Chennai
Java Certification in Delhi
Java Certification in Mumbai
Java Certification in Kolkata
Java Certification in Noida
Java Certification in Gurgaon
Java Certification in Ghaziabad
Online Java Training

Looking for Java Training Classes?

Learn from the Best Tutors on UrbanPro

Are you a Tutor or Training Institute?

Join UrbanPro Today to find students near you