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Ans. This looks like the case for optimistic locking wherein hibernate suspects that the information in table was updated by some other transaction after the entity was loaded by current transaction.
One way is to have synchronized entity state and don't detach the entity. Other could be to merge the entity with the table record rather than just directly persisting the entity.
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Ans. The objective of an abstract class is to provide an interface as well as code reuse. Though we cannot instantiate an instance of abstract class but we can reuse the code by extending such a class. Moreover abstract class provides interfacing to outside components just like interfaces.
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Q1624. If we don't provide any argument to the executed program, What arguments will be passed to the main method ? Will the String array argument be null ?
Ans. Constructors are used to initialize the state of an object. If there are no constructor , objects won't have any initialized state and hence it's elements may contain garbage values. If the memory were used as is, the behavior of the object would also be unpredictable.
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Ans. JVM (Java Virtual Machine) is an abstract machine. It is a specification that provides runtime environment in which java bytecode can be executed.JVMs are available for many hardware and software platforms (i.e. JVM is platform dependent).Runtime Instance Whenever you write java command on the command prompt to run the java class, an instance of JVM is createdThe JVM performs following operation:Loads codeVerifies codeExecutes codeProvides runtime environment
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Ans. Counter controlled repetitions are the loops that are controlled with the use of counters or the loops where the number of repetitions are known in advance. for loop in java is the counter controlled repetition.
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Ans. It's a programming technique wherein the method can call itself. The method call usually involves a different set of parameters as otherwise it would lead to an infinite loop. There is usually a termination check and statement to finally return the control out of all function calls.
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Ans. Yes, it's a project by confluent that provides in built mechanism for streaming records from bigdata data source to apache kafka message queues and vice versa. It provides a variety of source and sink connectors to achieve this.
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Ans. Source connectors are the connectors that are used to get information from the source whereas sink connectors are used to deploy information to the destination.
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Ans. it depends on the implementation of equals method of the respective class. If no definition is provided and it uses the default definition of the object class, two references are equal only if they point to the same object.
We can have such an equality defined for a particular class objects if we provide appropriate implementation of equals method comparing all those fields.
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Ans. The Web Services Description Language or WSDL is an XML based interface definition language that is used for describing the functionality offered by a web service.
WSDL holds information regarding communication policy, available methods, parameters it expects, and return types.
It's kind of a way to establish contract of communication between the client and service provider.
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Ans. RMI uses a standard mechanism for communicating with remote objects i.e stubs and skeletons. A stub for a remote object acts as a client's local representative. The caller invokes a method on the local stub which is responsible for carrying out the method call on the remote object.
Stub resides at the client that upon calling whose method results in establishing connection with the server, serializing and mar shelling the request and then waiting for the response whereas skelton resides at the server that receives the request, unmarshal it and then deserialize to fulfil the request.
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Ans. A sandbox is a testing environment that isolates untested code changes and outright experimentation from the production environment or repository.
It's an environment that's usually reserved for integration testing with external clients and modules with mock code so as to enable some sort of integration testing before the actual project is deployed.
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Ans. synchronized is a keyword and a modifier. The synchronized keyword is used to indicate that a method can be accessed exclusively by one thread at a time.
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Ans. Access modifiers are the java reserved keywords that changes the access privileges on a class , method , element etc. For example - public , private and protected.
Non Access modifiers are the java modifiers other than access modifiers. For example - static , final, abstract, synchronized, transient, volatile etc.
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Ans. Keyword is a reserved word that has a pre defined meaning for the compiler and hence cannot be used as an identifier, for example - final, private , for etc.
Identifier is the name given by the programmer to a programming construct, for example - class and method names etc.
java Keywords cannot be used as an identifier in java.
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