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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. 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. 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. 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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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. It's the way for synchronization wherein we can store version information in the table , so that if the same entity is updated by two transactions, the last to commit changes is informed of the conflict, and does not override the other transaction's work.
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Ans. Garbage collection mechanism frees up the memory that is no longer needed. In languages like C / C++ the deallocation needs to be done explicitly by the programmer and hence any leniency may result in memory leak. Garbage collection in java ensures that all unused memory is reclaimed and hence there are no memory leaks.Moreover it relieves the programmer from the hassle of carefully releasing all memory.
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Empty the 5 litre can into the 3 litre can leaving 2 litres in the 5 litre can.
Pour away the contents of the 3 litre can.Fill the 3 litre can with the 2 litres from the 5 litre can leaving 2 litres in the 3 litre can.
Fill the 5 litre can from the tap.Fill the remaining 1 litre space in the 3 litre can from the 5 litre can.Leaving 4 litres in the 5 litre can.
Number 2 -
Fill the 3 litre can from the tap.Empty the contents of the 3 litre can into the 5 litre can.
Fill the 3 litre can from the tap.Empty the contents of the 3 litre can into the 5 litre can leaving the 5 litre can full and 1 litre in the 3 litre can.
Pour away the contents of the 5 litre can. Pour the 1 litre from the 3 litre can into the 5 litre can.
Fill the 3 litre can from the tap. Empty the contents of the 3 litre can into the 5 litre can leaving 4 litres in the 5 litre can.
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Ans. A gobbler class take care of reading from a stream and optionally write out to another stream. Allows for non blocking reads when invoking a process through Runtime.exec(). Moreover the user can specify a callback that is called whenever anything is read from the stream.
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Ans. Application is unable to insert a record as it violates a unique constraint.
The exception states the constraint and Table can be located by the Entity mapping. So I will go to the DB and will first check to which all columns the unique constraint applies. And then I will go and check the code and logs to see how come the duplicate column values were attempted to be inserted when they were not supposed to be.
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Ans. We can declare the reference as final to avoid reassignment but again we can always initialize the final reference to null. Even if there was any such facility available , it would have meant poor use of resources by assigning a new object in memory to each reference that's created. Many a times references are just meant to refer to other objects which already have a reference i.e sharing object by multiple references.
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Ans. Null means nothing and hence means it's being assigned something till anything can be assigned to the reference. Null is a common memory location that get's assigned to any object reference till an actual object is assigned.
Empty object may not have a programmer initialized state but still a separate object in memory that has been assigned the placeholders.
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Ans. whenever a reference is created in Java without assigning the object
like
String str;
It get's assigned to null. So null provides a temporary memory location which any reference can point to till an appropriate object is assigned. Moreover it denotes that nothing has been assigned yet and hence provides a check in many cases.
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