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Q541. If we have more threads than partitions in a kafka consumer, How can we model it efficiently ?
Ans. We will have to use multiple consumer groups in that case as threads will remain idle if we use single consumer group. A more sophisticated algorithm could be required with multiple groups if we have to ensure the order of consumption.
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Q543. Can a lock be acquired on a class? How is it different than the object level lock ?
Ans. Yes, a lock can be acquired on the class. Class level lock is applicable on the whole class and hence on all objects of the class whereas the object level lock is applicable on the respective object.
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Ans. Associativity determines whether an expression is evaluated left-right or right-left. When an expression has two operators with the same precedence, the expression is evaluated according to its associativity.
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Ans. Hadoop is an open source framework , written in java by apche software foundation. This framework is used to write applications to process vast amount of data. Processing happens in parallel on large clusters which could have 1000 of computers. It processes data in a very reliable and fault tolerant manner.
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Ans. One common usage is predictive analytic using huge current or past data. For example - Using recent medical data ( diagnosis and procedure ), one can identify the pattern of diseases or the procedures that has to eventually applied upon certain diagnosis. This analysis might help in predicting the diseases that might occur to a patient.
the other usage could be to identify the future spending patterns of the population by analyzing the past and current habits.
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Ans. Combiners are used to increase the efficiency of a Map Reduce program. They are used to aggregate intermediate map output locally on individual mapper outputs. Combiners can help you reduce the amount of data that needs to be transferred across to the reducers.
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Ans. Stored procedures are a batch of SQL statements along with programming constructs ( if else, loops etc ) and stored as a single program that can be called by different clients and hence reused.
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Q555. Can we have try statement without catch? If try statement contains return will the finally block be executed? What happens if there is an exception inside finally block?
Q557. There is a Table Student having Student Id, Name and Total Marks. Can you please write an SQL that will display the maximum marks obtained by a student ?
Ans. DTO is Data Transfer Object i.e Pojo which is supposed to move between different layers of software architecture for transferring information. Example could be the object passed from client in case of web service call or the object passed to Persister for Database Persistence.
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Ans. DAO is Data Access Object which is used within Persistence Layer to make Database Transaction. For example , the class holding the Database connection and CRUD methods.
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Q564. If you are supposed to deprecate the method , Will you deprecate the method in the implementation class or will you deprecate the abstract declaration within interface or abstract class ?
Ans. Deprecating the interface / or declaration doesn't make much sense as the implementation is deprecated and not the interface.
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Q565. When do we generally get the database error - Unique Constraint Violated ?
Ans. This error can result either on an insert, update or delete when any change in data results in duplicate record or subset of it having unique constraint on record or its subset. For example - If we have a unique constraint on a combination of columns and then trying to insert duplicate column values.
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Ans. Audit Tables generally stores Raw information to be reviewed in case of problems or determining impact. If Database space is an issue , and the audit information is rarely retrieved, one design could be to use compressed file system.
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Ans. When a DML is executed, the changes only stays in session and still not pushed to DB Tables, Commit is used to push those changes to the Tables.
In case we realize that we don't want to commit those changes and would like to ignore them, we can use rollback.
For example - You may like that for a banking transaction you would like to update the account balance only if the debit or credit record was correctly inserted, so you may like to encapsulate both DML's - insert for transaction and update for balance in a single transaction and would only commit if both succeeds else rollback.
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Q569. Can I run a java program without creating any class ?
Ans. No, It requires creation of atleast one Class. Creating an object of that class is not compulsory as we can write all our logic within main method which is static.
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