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Ans. mutual exclusion i.e the resource is not shareable and hence a process should have exclusive access to it at a particular time
Hold and Wait i.e the process doesn't release all existing resources held by it before requesting for another one.
No preemption i.e noone can forcefully release a resource held by another process and the process should voluntarily release the resource held by it.
Circular Wait - For ex, P1 is waiting on resource to be released by P2, P2 is waiting on resource to be released by P3 and P3 is waiting on the resource to be released by P1
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Ans. Yes. Both concepts are independent of each other. Overriding depends on the methods with same name and signature whereas Overloading on same name but with different signatures. All definitions of an overloaded method can be individually overridden in the derived class.
For example -
Class A has overloaded methods "public void myMethod(String str)" and "public void myMethod(int x)"
We can have derived class ClassB extends ClassA and hence can override both methods myMethod(String str) and myMethod(int x) in ClassB
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Ans. dynamic method dispatch is a process in which a call to an
overridden method is resolved at runtime rather than at compile-time. This is used to achieve runtime polymorphism in java.
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Ans. Enumeration can iterate only legacy collections like Vector , HashTable and Stack whereas Iterator can iterate both legacy and non legacy collections.
Enumeration is less safer than Iterator
Enumeration is fail safe whereas Iterator is fail fast
Iterator allows for removal of element while traversal whereas Enumeration doesn't have remove method.
Enumerations were introduced in Java 1 whereas Iterators were introduced with Java 2
Enumerations have methods like hasMoreElements and nextElement whereas Iterators have methods like hasNext, next and remove
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Ans. Such a class still can have member elements which can be inherited and hence facilitate code reuse. Moreover Abstract class can have non final static elements whereas interfaces are only allowed to have static final elements.
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Q1002. How does java identifies which method to be called in method overriding or runtime polymorphism, when both methods share the same name and signature ?
Ans. runtime polymorphism or method overriding doesn't require method name and signature to be different whereas compile time polymorphism or method overloading requires method name to be same but the signature to be different.
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Q1004. How can you extract integers from string values and add (sum it up) all the extracted integers? e.g "James34long4island322in3rdAvenue" ---> 34 4 322 3 = 363
Ans. Abstract classes provide a mechanism of interfacing ( using abstract method ) as well as code reuse through inheritance ( extending abstract class )
Comparing to concrete class they have an advantage of providing interface which a concrete class doesn't provide.
Comparing to interfaces they have an advantage of providing code reuse through inheritance which interfaces dont provide.
Ans. If the number of input values is large, we can go about passing them as query params instead of path params. If the number is even larger and complex , its better to create a post service that behaves like a get service. Though this practice is not recommended but technically it can be accomplished.I dont mind doing it if the exceptionally large number of input would make it much more confusing.
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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. 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. 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. 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. Frankly saying I dont see much use of method overloading as its just little design convenience as you can use the same name but still have binding to different methods depending on the need.
Method overriding is really important and is much more useful than method overloading. Along with other programming concepts like interfaces and dependency injection , it facilitates the development of software as libraries and plug-gable components.
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