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Q:

What is an abstract class?

Answer

An abstract class is an incomplete class. An abstract class is defined with the keyword abstract . We cannot create an object of the abstract class because it is not complete. It sets a behavioral protocol for all its child classes.

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Subject: Java

Q:

What is the difference between a constructor and a method?

Answer

A constructor is a member function of a class that is used to create objects of that class. It has the same name as the class itself, has no return type, and is invoked using the new operator. We cannot invoke a constructor directly.


 


A method is an ordinary member function of a class. It has its own name, a return type (which may be void), and is invoked using the dot operator.

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Subject: Java

Q:

What is a class, member and local variable?

Answer

Variables declared within a method are local variables. Variables declared within the class are member variables.  Variables declared within the class with static modifier are class variables 

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Subject: Java

Q:

What is polymorphism?

Answer

It is the ability of an object to behave differently on different situations for the same message.

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Subject: Java

Q:

What is JAR file?

Answer

A JAR file (short for Java Archive) is a ZIP file used to distribute a set of Java classes. It is used to store compiled Java classes and associated metadata that can constitute a program

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Subject: Java

Q:

What is the difference between throw and throws clause?

Answer

A throw is used to throw an exception manually, where as throws is used in the case of checked exceptions, to tell the compiler that we haven't  handled the exception, so that the exception will be handled by the calling function.

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Subject: Java

Q:

When mapping a supertype/subtype relationship which of the following is true?

A) The supertype primary key is assigned to each subtype. B) The subtype primary key is assigned to each supertype.
C) There is no link between the supertype/subtype entities. D) There is no primary key/foreign key relationship between a supertype/subtype.
 
Answer & Explanation Answer: A) The supertype primary key is assigned to each subtype.

Explanation:
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Filed Under: Database

Q:

If no multivalued attributes exist and no partial dependencies exist in a relation, then the relation is in what normal form?

A) First normal form B) Second normal form
C) Third normal form D) Fourth normal form
 
Answer & Explanation Answer: B) Second normal form

Explanation:
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Filed Under: Database