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| Ans. HGETALL <key> | ||||
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 Discuss Correct / Improve  Redis check fields and value for a key | ||||
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| Ans. We can go to respective environment and check configuration and then scaling. It mentions that as current status like Current status: 2 instance(s) in service, Min: 1, Max: 4 | ||||
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| Discuss Correct / Improve AWS Amazon AWS Amazon EC2 Elastic Beanstalk Auto Scaling | ||||
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| Ans. It's a configuration for auto scaling environment that specify the attributes / conditions for scaling instances up and down. For example - We may like environment to scale up when the number of requests / sec increases a particular threshold and scale down when it decreases below a threshold. | ||||
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| Discuss Correct / Improve AWS Amazon AWS Amazon EC2 Elastic Beanstalk Auto Scaling Scaling Trigger production support | ||||
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| This question was recently asked at 'Dell'.This question is still unanswered. Can you please provide an answer. | ||||
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Discuss Correct / Improve producer consumer problem multi-process synchronization problem  Asked in 1 Companies | ||||
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| Ans. A partition key is used to group data by shard within a stream. A partition key identifies which shard the message belong to. | ||||
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| Discuss Correct / Improve Amazon AWS AWS Amazon Kinesis Stream shard shard in amazon kinesis partition key in amazon kinesis shard and partition key | ||||
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| Ans. A shard is a uniquely identified group of data records in a stream or we can say that Shard is a partition in Kinesis stream. A shard supports a fixed bandwidth i.e fixed number of messages per second. The total capacity of the stream is the sum of the capacities of its shards. If the data rate changes, we can allocate / deallocate more shards to accommodate that. | ||||
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| Discuss Correct / Improve Amazon AWS AWS Amazon Kinesis Stream shard shard in amazon kinesis | ||||
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| This question was recently asked at 'ECI Telecom'.This question is still unanswered. Can you please provide an answer. | ||||
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| Discuss Correct / Improve design design a coffee machine Asked in 1 Companies | ||||
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| Ans. OOPs or Object Oriented Programming is a Programming model which is organized around Objects instead of processes. Instead of a process calling series of processes, this model stresses on communication between objects. Objects that all self sustained, provide security by encapsulating it's members and providing abstracted interfaces over the functions it performs. OOP's facilitate the following features 1. Inheritance for Code Reuse 2. Abstraction for modularity, maintenance and agility 3. Encapsulation for security and protection 4. Polymorphism for flexibility and interfacing | ||||
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Discuss Correct / Improve oops oops features Asked in 260 Companies  basic  frequent | ||||
 Usually asked in relation to casting and ClassCastException. | ||||
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| Ans. The operator instanceOf is used to verify if the specified object is the instance of specified class or interface. Syntax if(x instanceOf ABC) where x is an object reference and ABC could be a class name or interface name. The above statement will be true if x holds an object that is an instance of ABC or any of the child class of ABC or if x holds an object that implements ABC. instanceOf operator is used to verify in case of downcasting. For ex - DerivedClass extends BaseClass x is the reference of BaseClass but holds DerivedClass object ( Polymorphism ) There is an operation that is defined in Derived Class, let's say derivedClassMethod() We cannot call derivedClassMethod() directly using x as x is reference of BaseClass and not DerivedClass and hence can only access methods that are defined in BaseClass and overridden in derived class. Though we can cast it to DerivedClass as following ((DerivedClass)x).derivedClassMethod(); But it may throw ClassCastException in case x doesn't hold an instance of DerivedClass at that point. So before casting it to DerivedClass we may like to make sure that it is an instance of DerivedClass and hence won't throw ClassCastException. So we make a check for it if(x instanceOf DerivedClass) { ((DerivedClass)x).derivedClassMethod(); } | ||||
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| Discuss Correct / Improve instanceOf instanceOf operator Why we need instanceOf operator use of instanceOf operator Asked in 2 Companies Intermediate frequent | ||||
| Very frequently asked. Usually among very first few questions. | ||||
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| Ans. Encapsulation is a feature of OOP's that binds the data and it's associated methods together as a single unit and facilitate protection and data hiding by providing minimal interface to outside. For example - member variables are declared private and are accessed through public methods. Moreover we have private methods that can only be used internally and hence providing minimal interface to outside class through use of public methods. | ||||
 Sample Code for encapsulation | ||||
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| Discuss Correct / Improve encapsulation object oriented programming (oops) oops concepts oops oops concepts oops features Asked in 4 Companies Basic frequent | ||||
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| This question was recently asked at 'Ola Cabs'.This question is still unanswered. Can you please provide an answer. | ||||
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| Discuss Correct / Improve program code coding insertion sort sort Asked in 1 Companies | ||||
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| Ans. int compare(int a, int b) { a>b? return a: return b; } | ||||
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| Discuss Correct / Improve code program coding Asked in 1 Companies basic | ||||
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| Ans. We can copy the elements to a Set and then find the difference of count between ArrayList and Set. As Set don't allow duplicates , they will be removed in the set. | ||||
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| Discuss Correct / Improve collections arraylist set | ||||
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| Ans. ArrayLists aren't synchronized and hence doesn't allow synchronized access. As multiple threads can access an arraylist in parallel, it may result in an inconsistent state. | ||||
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| Discuss Correct / Improve vector arraylist list collections Basic | ||||
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| Ans. It means that only 1 thread can access have access to Vector at a time and no parallel access is allowed whereas Array List allows parallel access by multiple threads. | ||||
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| Discuss Correct / Improve vectors arraylist collections list synchronization synchronized | ||||
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| Ans. Because it's access isn't synchronized and hence access / modification by multiple threads may lead to inconsistent state. | ||||
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| Discuss Correct / Improve fail fast arraylist collections | ||||
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| Ans. Java Programs are collection of objects that communicates with each other to get a task accomplished. To add to those objects, there are common spaces ( static i.e common for objects belonging to a class ) that are used too. We can visualize objects as departments of an organization in real world. Just like Task gets initiated in one department and then files are moved across different departments to get work done. In a similar fashion, a task is initiated in one object ( having main method ) and then information ( through POJOs / DTOs ) is moved across objects to accomplish a task. | ||||
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| Discuss Correct / Improve objects Java Programs are collection of objects real life example of object communication | ||||
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| Ans. final keyword is a modifier that means differently when applied to variables, methods and classes. 1. Final variable cannot be changed once initialized 2. Final method cannot be overridden 3. Final class cannot be sub classed | ||||
| Sample Code for final variable Sample Code for final method Sample Code for final class | ||||
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| Discuss Correct / Improve final final keyword Asked in 1 Companies Basic frequent | ||||
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| Ans. By encapsulating it within another class and declaring it private. In such a case, it will only be accessible through parent class or parent class object. | ||||
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| Discuss Correct / Improve private class private inner class class hiding encapsulation object oriented programming (oops) oops concepts inner classes nested classes | ||||
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| Ans. Making an outer class as private will make it inaccessible from anywhere and would make it useless. | ||||
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| Discuss Correct / Improve private variables | ||||
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| Ans. We can declare an inner class as private and hence would be restricting it's access from outside. We cannot make outer class as private. | ||||
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| Discuss Correct / Improve private class inner classes nested classes | ||||
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| Ans. Private variables are not inherited. They are simply ignored and not made part of the derived object body. | ||||
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| Discuss Correct / Improve private variables inheritance object oriented programming (oops) oops concepts | ||||
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| Ans. Single instance means there is only 1 instance that will bear all the traffic load whereas Load balanced server means that there will be a cluster of servers that will host the application and load will be balanced distributed among them. Auto Scaling means that the number of instances will be expanded / shrunken based on the rule. Rule could be the traffic count , response time etc. | ||||
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| Discuss Correct / Improve load balancing auto scaling aws elastic beanstalk | ||||
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| Ans. Load Balancing is a provision to improve performance by reducing load on a single machine / server. Traffic or load is distributed among different machines and hence resulting in better performance / response time by leveraging more resources. Failover is a provision to achieve better availability by switching to a backup server in case of failure. Load Balancing aims as improving performance whereas failover aims at improving availability. We can achieve both together by using a Load Balancing system which will isolate an instance in case of it's failure. | ||||
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| Discuss Correct / Improve load balancing failover load balancing vs failover production support | ||||
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| Ans. Boxing conversion converts expressions of primitive type to corresponding expressions of reference type. For example boolean to Boolean long to Long double to Double | ||||
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| Discuss Correct / Improve data type boxing wrapper classes | ||||
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| Ans. Conversion means that the expression / literal / value of one type getting converted to other type. Widening conversion is the conversion from Type A to Type B where B requires a wider space than A. For example - int to long, float to double, char to String etc. As the value moves to a wider space, there is no loss of information. Narrowing conversion is the conversion from Type A to Type B where B requires a narrower space space than A. For example - int to long, float to double, char to String etc.As the value moves to a narrower space, there is a loss of information. | ||||
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| Discuss Correct / Improve data type widening conversion narrowing conversion | ||||
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| Ans. Amazon CloudWatch is a monitoring service for AWS cloud resources like Beanstalk and DB instances. We can use CloudWatch to monitor the state of resources, collect metrices, set alarms and appropriate response to the alarm state. | ||||
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| Discuss Correct / Improve aws cloudwatch amazon cloudwatch aws | ||||
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| Ans. Web Server and Worker | ||||
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| Discuss Correct / Improve elastic beanstalk | ||||
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| Ans. We can do it by either going to Elastic Beanstalk -> Respective instance -> Logs or using CloudWatch -> Logs -> Respective Log Group | ||||
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| Discuss Correct / Improve aws logs cloudwatch logs elastic beanstalk | ||||
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| Ans. EC2 is Amazon computing service whereas Elastic Beanstalk is the AWS service for deploying and managing web applications. | ||||
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| Discuss Correct / Improve Elastic Compute Cloud EC2 Elastic Beanstalk | ||||
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