Core Java - Interview Questions and Answers for 'Object creation' | Search Interview Question

Core Java - Interview Questions and Answers for 'Object creation' - 6 question(s) found - Order By Rating

Q1. Does Constructor creates the object ?

Ans. New operator in Java creates objects. Constructor is the later step in object creation. Constructor's job is to initialize the members after the object has reserved memory for itself.

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Q2. Describe what happens when an object is created in Java ?

Core Java

Ans. 1. Memory is allocated from heap to hold all instance variables and implementation-specific data of the object and its superclasses. Implemenation-specific data includes pointers to class and method data.
2. The instance variables of the objects are initialized to their default values.
3. The constructor for the most derived class is invoked. The first thing a constructor does is call the constructor for its superclasses. This process continues until the constructor for java.lang.Object is called,as java.lang.Object is the base class for all objects in java.
4. Before the body of the constructor is executed, all instance variable initializers and initialization blocks are executed. Then the body of the constructor is executed. Thus, the constructor for the base class completes first and constructor for the most derived class completes last.

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Q3. Difference between Class#getInstance() and new operator ?

Ans. Class.getInstance doesn't call the constructor whereas if we create an object using new operator , we need to have a matching constructor or copiler should provide a default constructor.

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Q4. What are different ways of object creation in Java ?

Core Java

Ans. Using new operator - new xyzClass()

Using factory methods - xyzFactory.getInstance( )

Using newInstance( ) method - (Class.forName(xyzClass))emp.newInstance( )

By cloning an already available object - (xyzClass)obj1.clone( )

Sample Code for object initialization using clone

Sample Code for object initialization using getInstance

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Q5. In a case where there are no instance variables what does the default constructor initialize?

Core Java

Ans. Java expects the superclass ( Object Class ) constructor to be called while creation of any object. So super constructor is called in case there are no instance variables to initialize.

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Q6. Difference between new operator and Class.forName().newInstance() ?

Ans. new operator is used to statically create an instance of object. newInstance() is used to create an object dynamically ( like if the class name needs to be picked from configuration file ). If you know what class needs to be initialized , new is the optimized way of instantiating Class.

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