In Java, is the statement "There is one default constructor in every class" always correct, or can a class legally have no default constructor?

Introduction / Context:
Constructors control how objects are created in Java. A common beginner rule states that every class has a default constructor. However, that statement is incomplete and can easily lead to confusion in real projects. This question asks you to evaluate the claim and understand exactly when the Java compiler provides a default no argument constructor and when it does not.

Given Data / Assumptions:

• Java classes can declare one or more constructors with parameters.
• If no constructor is declared, the compiler may generate a default one.
• A default constructor is a no argument constructor that simply calls the superclass no argument constructor.
• We are considering standard class definitions, not special cases such as records.

Concept / Approach:
The correct rule is that if a class declares no constructors at all, the Java compiler automatically provides a default no argument constructor. This synthetic constructor calls the superclass no argument constructor. However, as soon as you declare any constructor, with or without parameters, the compiler does not generate a default one for you. If you want a no argument constructor as well, you must declare it explicitly. Therefore, it is not accurate to say that every class always has a default constructor; many classes in real code bases have only parameterised constructors and no default.

Step-by-Step Solution:
Step 1: Consider a simple class with no constructors declared; the compiler adds a default no argument constructor automatically.Step 2: Now declare a constructor that takes parameters in the same class; the compiler assumes you are in full control.Step 3: In this second case, the compiler does not create any extra constructor, so there may be no no argument constructor at all.Step 4: Recognise that many frameworks require an explicit public no argument constructor when they use reflection, because it might not exist otherwise.Step 5: Conclude that the original blanket statement is false; the presence of a default constructor depends on whether other constructors are declared.

Verification / Alternative check:
You can verify this behaviour by compiling a class with a single parameterised constructor and then attempting to create an instance with new ClassName(). The compiler will report that no suitable constructor is found. Adding an explicit no argument constructor fixes the error, demonstrating that the compiler did not generate one automatically. Java language specifications also describe the rule for default constructors in these terms.

Why Other Options Are Wrong:
Option A ignores the important condition that a default constructor is generated only when no constructors are declared at all. Option C claims that both A and B are valid simultaneously, which is logically inconsistent because they contradict each other. Option D suggests that none of the explanations match Java behaviour, but option B precisely captures the rule. Therefore, B is the only correct choice.

Common Pitfalls:
A common pitfall is adding a parameterised constructor to a JavaBean or entity class and forgetting to add a no argument one. Frameworks that instantiate classes reflectively often fail with obscure error messages in this situation. Another issue is assuming that adding new constructors will never break existing client code. Understanding how default constructors are created or omitted helps you design classes that are easier to use and integrate with frameworks.

Final Answer:
Correct answer: The statement is false, a class can have no default constructor if you declare your own constructors