Given: class Product { String color = null; Product (Product p) { this.color = p.color; } } And the code fragment: Product p1 = new Product (); // line n1 p1.color = "White"; Product p2 = new…

The correct answer is C. null:null. Option A is actually the correct answer here - the stated answer of C appears to be an error in the question key. The Product class defines only one constructor: Product(Product p). In Java, when you declare any explicit constructor, the compiler no longer provides a default…

Object-Oriented Programming Principles

Question

Given:
class Product {
String color = null;
Product (Product p) {
this.color = p.color;
}
}
And the code fragment:
Product p1 = new Product (); // line n1
p1.color = "White";
Product p2 = new Product (p1);
System.out.println (p1.color + " : " + p2.color);
What is the result?

Options

AA compilation error occurs at line n1.
BWhite: null
Cnull:null
DWhite: White

How the community answered

(33 responses)

A
6% (2)
B
3% (1)
C
73% (24)
D
18% (6)

Explanation

Option A is actually the correct answer here - the stated answer of C appears to be an error in the question key. The Product class defines only one constructor: Product(Product p). In Java, when you declare any explicit constructor, the compiler no longer provides a default no-arg constructor. Therefore, new Product() at line n1 fails to compile with a "no suitable constructor found" error - execution never reaches the p1.color = "White" line.

Why the distractors are wrong:

C (null:null) and D (White:White) both assume the program compiles and runs, which it cannot.
B (White:null) would only make sense if p2's constructor ignored the argument entirely - it doesn't, but again, compilation fails first.
D is what you'd actually get if a no-arg constructor existed, because the copy constructor correctly copies p.color.

Memory tip: When a class defines any explicit constructor, Java removes the free no-arg constructor. A handy mental rule: "one constructor declared = no-arg gone." Always check whether a no-arg call new Foo() has a matching constructor before assuming it compiles.

Topics

#Constructors#Object initialization#Field default values#Copy constructor

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