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INTERVIEW QUESTIONS (JAVA DEVELOPER)
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INTERVIEW QUESTIONS (JAVA DEVELOPER)
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INTERVIEW QUESTIONS (JAVA DEVELOPER)What is a immutable class? - answer- A defined class where state of the object cannot be modified.
What is the default sorting order in TreeMap? - answer- Natural Ordering
What are marker interfaces? - answer- serializable, Cloneable, Remote , these interfaces have not implementation.
What is complexity ? - answer- Time and space measured for an algorithm
What is a disadvantages of indexes. If more then two columns are indexed in the same table. - answer- indexes occupies on memory , a lot of indexes can take up too much memory.
What is a composition ? - answer- Its a " has a " relation class A has a Class B object
Spring mvc , how does it work ? explain the mvc pattern - answer- uses the dispatcher servlet to take requests, goes through mapping , controller, view resolver and then view (which will be the response) to the dispatcher servlet
How to make a webservice secure? - answer- You can use Spring security to secure endpoints of controllers.
How to provide security with ssl ? - answer- Need certificate and ssl enabled on different port
Difference between hibernate save and commit - answer- session.save will create the row in the table to put data in but not commit. it will save the session. Works in a transnational way . Commit will actually commit the row and persist data.
Purpose of Atomic variables - answer- Atomic variables like AtomicInteger are syncronized / thread safe to use.
What is a externalization interface. - answer- Externalization extends serialization and has two methods , write externalize and read externalize.
JDBC statements. Explain Each - answer- Statement : not precompiled statement . does not protect you from SQL injection Prepared Statesmen: Are precompiled statements , prevents SQL injection. Contains parameters with " ?" to insert values to. Callable Statement : Used for stored Procedures.
What is a sequence in Oracle - answer- sequence is used when a row is added , the ID generated in a sequence.
What is a stored Procedure. - answer- Stored procedures a bunch of SQL statements that get executed.
Left Outer join example and SQL - answer- contains all elements from table A but no equal elements and table B elements. SQL : select A.columnName B.columnName from Table A
left join table B on A.columnName =B.columnName where B.columnName = null;
What are web service ? - answer- Web services are API used by third parties. exposes endpoints to use the api , Web services can be created from Restful Service , or SOAP.
What is a abstract factory pattern ? - answer- Abstract factory pattern is used to create all factories in one place. Its a Factory of factories.
GET PUT POST DELETE PUT , WHICH one is Idempotent - answer- PUT is idempotent. It can be called multiple times the outcome will be different.
Equi join ,natural join , cross join ,left outer join ,right outer join - answer- Equi join returns matching columns from Table A and B . Natural join return equi join and prints columns with the same name only once. Cross join return you the Cartesian product of two joins
left outer join return you the Table A and not Table B/ A equal Value and Table B values
right outer join , vice versa from above.
What is the default join - answer- inner join
What is the use of autowiring. - answer- used to inject dependencies to a class
What is AOP - answer- Aspect Oriented Programming, moduralizes cross cutting concerns
Inheritance: Can inherit properties / behaviors of the parent class by using the extend keyword. Polymorphism: I used to take a form of an object of another.
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