Java Interview Question

 

Does constructor return any value?

Ans: yes, The constructor implicitly returns the current instance of the class (You can't use an explicit return type with the constructor). More Details.

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Is constructor inherited?

No, The constructor is not inherited.

32) Can you make a constructor final?

No, the constructor can't be final.

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33) Can we overload the constructors?

Yes, the constructors can be overloaded by changing the number of arguments accepted by the constructor or by changing the data type of the parameters. Consider the following example.

1. class Test   
2. {  
3.     int i;   
4.     public Test(int k)  
5.     {  
6.         i=k;  
7.     }  
8.     public Test(int k, int m)  
9.     {  
10.         System.out.println("Hi I am assigning the value max(k, m) to i");  
11.         if(k>m)  
12.         {  
13.             i=k;   
14.         }  
15.         else   
16.         {  
17.             i=m;  
18.         }  
19.     }  
20. }  
21. public class Main   
22. {  
23.     public static void main (String args[])   
24.     {  
25.         Test test1 = new Test(10);  
26.         Test test2 = new Test(12, 15);  
27.         System.out.println(test1.i);  
28.         System.out.println(test2.i);  
29.     }  
30. }  
31.       

In the above program, The constructor Test is overloaded with another constructor. In the first call to the constructor, The constructor with one argument is called, and i will be initialized with the value 10. However, In the second call to the constructor, The constructor with the 2 arguments is called, and i will be initialized with the value 15.

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34) What do you understand by copy constructor in Java?

There is no copy constructor in java. However, we can copy the values from one object to another like copy constructor in C++.

There are many ways to copy the values of one object into another in java. They are:

• By constructor
• By assigning the values of one object into another
• By clone() method of Object class

In this example, we are going to copy the values of one object into another using java constructor.

1. //Java program to initialize the values from one object to another  
2. class Student6{  
3.     int id;  
4.     String name;  
5.     //constructor to initialize integer and string  
6.     Student6(int i,String n){  
7.     id = i;  
8.     name = n;  
9.     }