Technical Design Flashcards
What is software development Life Cycle (SDLC)? Where exactly the Testing activities begin in SDLC?
Analysis of demands Design Encoding Test The Implementation Maintenance
Strength testing starting with the initial state, i.e. the requirement analysis.
SDLC describes the order in which phase of the software and the software life cycle phase.
The test is dependent on a template used in the item tracking list waterfall research takes place after the coding and testing model XP-the whole development analysis and software requirements.
What is Diff. between STLC and SDLC?
Requirement analysis Design Encoding Test Maintenance
If the test-cycle testing phases of the SDLC software IE STLD-right part of the picture. I have the download stage:
Create test Data preparation when you write a test script Run test with test and numbers. If you have error is increased in the implementation of the Error when multiple finds to be resolved
What is the Different Software Development Model?
Life cycle (SDLC) system development The prototype model Application development model Component model building groups
Give an example where you prefer abstract class over interface ?
This is common but yet tricky design interview question. both interface and abstract class follow “writing code for interface than implementation” design principle which adds flexibility in code, quite important to tackle with changing requirement. here are some pointers which help you to answer this question:
- In Java you can only extend one class but implement multiple interface. So if you extend a class you lost your chance of extending another class.
- Interface are used to represent adjective or behavior e.g. Runnable, Clonable, Serializable etc, so if you use an abstract class to represent behavior your class can not be Runnable and Clonable at same time because you can not extend two class in Java but if you use interface your class can have multiple behavior at same time.
- On time critical application prefer abstract class is slightly faster than interface.
- If there is a genuine common behavior across the inheritance hierarchy which can be coded better at one place than abstract class is preferred choice. Some time interface and abstract class can work together also where defining function in interface and default functionality on abstract class.
Design a Vending Machine which can accept different coins, deliver different products?
This is an open design question which you can use as exercise, try producing design document, code and Junit test rather just solving the problem and check how much time it take you to come to solution and produce require artifacts, Ideally this question should be solve in 3 hours, at least a working version.
You have a Smartphone class and will have derived classes like IPhone, AndroidPhone,WindowsMobilePhone can be even phone names with brand, how would you design this system of Classes.
This is another design pattern exercise where you need to apply your object oriented design skill to come with a design which is flexible enough to support future products and stable enough to support changes in existing model.
When do you overload a method in Java and when do you override it ?
Rather a simple question for experienced designer in Java. if you see different implementation of a class has different way of doing certain thing than overriding is the way to go while overloading is doing same thing but with different input. method signature varies in case of overloading but not in case of overriding in java.
Design ATM Machine ?
We all use ATM (Automated Teller Machine) , Just think how will you design an ATM ? for designing financial system one must requirement is that they should work as expected in all situation. so no matter whether its power outage ATM should maintain correct state (transactions), think about locking, transaction, error condition, boundary condition etc. even if you not able to come up exact design but if you be able to point out non functional requirement, raise some question , think about boundary condition will be good progress.
You are writing classes to provide Market Data and you know that you can switch to different vendors overtime like Reuters, wombat and may be even to direct exchange feed , how do you design your Market Data system.
Reuters, wombat and may be even to direct exchange feed , how do you design your Market Data system.
This is very interesting design interview question and actually asked in one of big investment bank and rather common scenario if you have been writing code in Java. Key point is you will have a MarketData interface which will have methods required by client e.g. getBid(), getPrice(), getLevel() etc and MarketData should be composed with a MarketDataProvider by using dependency injection. So when you change your MarketData provider Client won’t get affected because they access method form MarketData interface or class.
Why is access to non-static variables not allowed from static methods in Java
You can not access non-static data from static context in Java simply because non-static variables are associated with a particular instance of object while Static is not associated with any instance. You can also see my post why non static variable are not accessible in static context for more detailed discussion.
Design a Concurrent Rule pipeline in Java?
Concurrent programming or concurrent design is very hot now days to leverage power of ever increasing cores in advanced processor and Java being a multi-threaded language has benefit over others. Do design a concurrent system key point to note is thread-safety, immutability, local variables and avoid using static or instance variables. you just to think that one class can be executed by multiple thread a same time, So best approach is that every thread work on its own data, doesn't interfere on other data and have minimal synchronization preferred at start of pipeline. This question can lead from initial discussion to full coding of classes and interface but if you remember key points and issues around concurrency e.g. race condition, deadlock, memory interference, atomicity, ThreadLocal variables etc you can get around it.
What is design patterns ? Have you used any design pattern in your code ?
Design patterns are tried and tested way to solve particular design issues by various programmers in the world. Design patterns are extension of code reuse.
Can you name few design patterns used in standard JDK library?
Decorator design pattern which is used in various Java IO classes, Singleton pattern which is used in Runtime , Calendar and various other classes, Factory pattern which is used along with various Immutable classes likes Boolean e.g. Boolean.valueOf and Observer pattern which is used in Swing and many event listener frameworks.
What is Singleton design pattern in Java ? write code for thread-safe singleton in Java
Singleton pattern focus on sharing of expensive object in whole system. Only one instance of a particular class is maintained in whole application which is shared by all modules. Java.lang.Runtime is a classical example of Singleton design pattern. You can also see my post 10 questions on Singleton pattern in Java for more questions and discussion. From Java 5 onwards you can use enum to thread-safe singleton.
What is main benefit of using factory pattern ? Where do you use it?
Factory pattern’s main benefit is increased level of encapsulation while creating objects. If you use Factory to create object you can later replace original implementation of Products or classes with more advanced and high performance implementation without any change on client layer. See my post on Factory pattern for more detailed explanation and benefits.
