Given: class Bus { String type = "default"; // line n1 Bus (String type) { // line n2 this.type = type; } } public class App{ public static void main(String[] args) { Bus b1 = new Bus()…

The correct answer is C. The code fails to compile. To make it compile, at line n1 insert: Bus() {}. Option C is correct because Java only provides a default no-arg constructor when no constructors are explicitly defined. Since Bus already declares Bus(String type), the compiler removes the implicit no-arg constructor, causing new Bus() in main to fail - and the fix is to…

Object-Oriented Programming Principles

Question

Given:
class Bus {
String type = "default";
// line n1
Bus (String type) {
// line n2
this.type = type;
}
}
public class App{
public static void main(String[] args) {
Bus b1 = new Bus();
System.out.println(b1.type);
Bus b2 = new Bus("luxury");
System.out.println (b2.type);
}
}
What is the result?

Options

AThe code fails to compile. To make it compile, at line n1 insert: this() {}
BThe code fails to compile. To make it compile, at line n2 insert: this();
CThe code fails to compile. To make it compile, at line n1 insert: Bus() {}
DThe code compiles and prints: default luxury

How the community answered

(36 responses)

A
8% (3)
B
3% (1)
C
86% (31)
D
3% (1)

Explanation

Option C is correct because Java only provides a default no-arg constructor when no constructors are explicitly defined. Since Bus already declares Bus(String type), the compiler removes the implicit no-arg constructor, causing new Bus() in main to fail - and the fix is to explicitly declare Bus() {} at line n1.

Option A is wrong because this() {} is not valid constructor declaration syntax; this(...) is a constructor invocation (used to call one constructor from another), not a declaration. Option B is wrong because inserting this() inside the parameterized constructor would attempt to call a no-arg constructor that still doesn't exist, so compilation still fails. Option D is wrong because the code does not compile in its current state - new Bus() has no matching constructor.

Memory tip: Think of it as the compiler's "gift" - it gives you a free no-arg constructor only when you ask for nothing. The moment you define any constructor yourself, the gift is gone and you must provide your own no-arg constructor explicitly if you need one.

Topics

#constructors#default constructor#constructor overloading#object instantiation

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