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Ans. All Keywords , modifiers ( public , static , final etc ) as well as non modifier keywords ( for, if,switch etc ) are reserved words in java and hence cannot be used as identifiers. Along with keywords , there are few literals that have predefined meaning and hence cannot be used as identifiers, these are true , false and null.
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Ans. Population of Manhattan is roughly 2 millions. Nearly same number of people come to Manhattan daily for work. So if whole of Manhattan comprise of only residential and commercial buildings, that makes up 1/3rd residential and 2/3rd commercial. I have lived in a house in a high rise building in downtown and the average size of the house is 1 bedroom with 2 windows and on average 2 people live in a house. So that makes up roughly 1.33 million windows in Residential buildings. At commercial buildings, windows per capita is much lower as more people share the space and roughly it comes down to 1 window for 10 people. So that makes up .266 millions windows in commercial establishments.
So in total there are roughly 1.6 million windows in Manhattan.
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Ans. Amazon Elastic Compute Cloud or EC2 provides scalable computing capacity in the AWS cloud. It can be used to create Virtual Environments , storage and configure. EC2 enables to upgrade or downgrade infrastructure according to the rules defined ( with fluctuation in latency, traffic etc )
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Ans. Latency is the delay incurred while communicating a message i.e the time took the message in transit over network.
processing time is the delay it took for the server to process the request.
Response time is the sum total of latency and processing time.
For example -
Let's say it takes 1 ms for the request to reach from client to server and similar 1 ms for the response to come back to client. Moreover it takes approx 10 ms for the application to process the request. So The response time would be outward latency + processing time + inward latency = 12 ms
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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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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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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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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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LikeDiscussCorrect / Improve private class private inner class class hiding encapsulation object oriented programming (oops) oops concepts inner classes nested classes
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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LikeDiscussCorrect / Improve objects Java Programs are collection of objects real life example of object communication
Q1878. Why iterators of an array list are fail fast ?
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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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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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.
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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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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LikeDiscussCorrect / Improve AWS Amazon AWS Amazon EC2 Elastic Beanstalk Auto Scaling Scaling Trigger production support
Q1889. How can we know how many instances are currently in service within an Elastic Beanstalk environment ?
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