Java_Constructor_1

Q1  : What is a Constructor?
Ans : Constructors are used to initialize the object’s state. Like methods, a constructor also contains collection of statements(i.e. instructions) 
that are executed at 
      time of Object creation.
      
 Q2  : Do we have Copy Constructor in Java?
 Ans : Java also supports copy constructor. But, unlike C++, Java doesn’t create a default copy constructor if you don’t write your own.
 To copy the values of one object into another in java, you can use:
              Constructor
              Assigning the values of one object into another
              clone() method of Object class
              
Q3  : What is Constructor Chaining ?
Ans : Constructor Chaining is a technique of calling another constructor from one constructor. this() is used to call same class constructor where as super() is used
to call super class constructor.

Q4  : Can we call sub class constructor from super class constructor?
Ans : No. There is no way in java to call sub class constructor from a super class constructor.

Q5  : What happens if you keep a return type for a constructor?
Ans : Ideally, Constructor must not have a return type. By definition, if a method has a return type, it’s not a constructor.(JLS8.8 Declaration) 
It will be treated as a normal method. 
      But compiler gives a warning saying that method has a constructor name.

Q6  : What is No-arg constructor?
Ans : Constructor without arguments is called no-arg constructor. Default constructor in java is always a no-arg constructor.

Q7  : How a no – argument constructor is different from default Constructor?
Ans : If a class contains no constructor declarations, then a default constructor with no formal parameters and no throws clause is implicitly declared.
If the class being declared is the primordial class Object, then the default constructor has an empty body. Otherwise, the default constructor simply 
invokes the superclass constructor with no arguments.

Q8  : What are private constructors and where are they used?
Ans : Like any method we can provide access specifier to the constructor. If it’s made private, then it can only be accessed inside the class.
      The major scenarios where we use private constructor:
                Internal Constructor chaining
                Singleton class design pattern

Q9  : When do we need Constructor Overloading?
Ans : Sometimes there is a need of initializing an object in different ways. This can be done using constructor overloading. Different constructors
can do different work by implementing different line of 
      codes and are called based on the type and no of parameters passed. According to the situation , a constructor is called with specific number 
      of parameters among overloaded constructors.
      
Q10 : Do we have destructors in Java?
Ans : No, Because Java is a garbage collected language you cannot predict when (or even if) an object will be destroyed. Hence there is no direct equivalent
of a destructor.