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mock question

 
Greenhorn
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What will happen if you compile/run the following code?

1: public class Q21
2: {
3: int maxElements;
4:
5: void Q21()
6: {
7: maxElements = 100;
8: System.out.println(maxElements);
9: }
10:
11: Q21(int i)
12: {
13: maxElements = i;
14: System.out.println(maxElements);
15: }
16:
17: public static void main(String[] args)
18: {
19: Q21 a = new Q21();
20: Q21 b = new Q21(999);
21: }
22: }
A) Prints 100 and 999.
B) Prints 999 and 100.
C) Compilation error at line 3, variable maxElements was not initialized.
D) Compillation error at line 19.
The correct answer is D
Could someone explain why.
thanks in adv
amisha
 
Ranch Hand
Posts: 50
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Hi Amisha,
The Correct answer is D. Compilation Error at Line 19.
This is because there is no default constructor in class Q21. So when u r trying to instantiate an object a at line 19 of class Q21, the compiler will complain regarding no matching constructor found in Class Q21.
Default constructors are provided only if u do not define any other constructors in u're class. The other thing which u must have been confused is the method which is declared at line 5. It is perfectly legal to declare a method as the same name as the class. It is not a constructor. I hope u understand.
All the best.
Amit
 
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hi
ans constructors dont have the return type void
please remove the void from the default constructor Q21()
now it will run
 
Amit Punjwani
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Bala,
I think u r mistaken by line 5. The declaration at line 5 is not a constructor but it is a method. As I said earlier it is perfectly legal to define a method with the same name as the class name.
If u want the above code to run just define a no-argument constructor
<pre>
public class Q21
{
int maxElements;
Q21() {
System.out.println("No argument constructor");
}
void Q21()
{
maxElements = 100;
System.out.println(maxElements);
}

Q21(int i)
{
maxElements = i;
System.out.println(maxElements);
}
public static void main(String[] args)
{
Q21 a = new Q21();
Q21 b = new Q21(999);
}
}
</pre>
The code will now compile fine
Any problems will be pleased to solve.

------------------
 
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Hello
A Patel
The constructor doesn't have any return type.Constructor can be only public,private,protected and can throw an exception.The name of constructor is same as name of class and doesn't have any return type.
Hope this things cleared your dought.
I'm SCJP now if you need help mail me on this mail id sanjaypts@yahoo.com

Thanx
sp
 
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