Quick Answer
The answer is the `abstract` modifier because an abstract class cannot be instantiated in Java, yet it remains fully extendable by subclasses. This design constraint is enforced at the compiler level: any attempt to use the `new` keyword on an abstract class triggers a compilation error, ensuring that `Shape` serves only as a blueprint for concrete types like `Circle` or `Rectangle`. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this concept tests your understanding of abstraction and inheritance, often appearing in questions that contrast `abstract` with `final` or `private` modifiers—common traps where candidates mistakenly choose `final` (which prevents extension) or a private constructor (which blocks subclassing entirely). Remember that `abstract` is the only modifier that simultaneously prohibits instantiation while permitting inheritance. A useful mnemonic: "Abstract says 'no objects, yes children'."
This 1Z0-829 practice question tests your understanding of utilizing java object-oriented approach. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A developer needs to ensure that a class `Shape` cannot be instantiated but can be extended. Which modifier should be used?
private
Why wrong: A class cannot be private, only inner classes can. But even with private constructor, the class can still be instantiated via static methods, and it cannot be extended.
final
Why wrong: Final prevents extension, not instantiation.
abstract
Abstract classes cannot be instantiated and are meant to be extended.
sealed
Why wrong: Sealed classes can be instantiated directly unless declared abstract.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
abstract
The `abstract` modifier is correct because an abstract class cannot be instantiated directly, but it can be extended by subclasses. This enforces the design intent that `Shape` serves as a base class for specific shapes like `Circle` or `Rectangle`, while preventing the creation of a generic `Shape` object.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
private
Why it's wrong here
A class cannot be private, only inner classes can. But even with private constructor, the class can still be instantiated via static methods, and it cannot be extended.
final
Why it's wrong here
Final prevents extension, not instantiation.
abstract
Why this is correct
Abstract classes cannot be instantiated and are meant to be extended.
Related concept
Read the scenario before looking for a memorised answer.
sealed
Why it's wrong here
Sealed classes can be instantiated directly unless declared abstract.
Common exam traps
The trap here is that candidates often confuse `abstract` with `final` or `sealed`, mistakenly thinking that preventing instantiation requires a modifier that blocks extension, when in fact `abstract` is the only modifier that both prevents instantiation and allows extension.
Detailed technical explanation
In Java, an abstract class is declared with the `abstract` keyword and may contain abstract methods (without a body) that must be implemented by concrete subclasses. Under the hood, the JVM prevents instantiation of abstract classes by throwing a `java.lang.InstantiationError` if an attempt is made via `new`. This is commonly used in frameworks like Java AWT's `Component` class, which is abstract to provide a common base for GUI elements while forcing subclasses to define specific behavior.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 1Z0-829 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Utilizing Java Object-Oriented Approach — This question tests Utilizing Java Object-Oriented Approach — Read the scenario before looking for a memorised answer..
The correct answer is: abstract — The `abstract` modifier is correct because an abstract class cannot be instantiated directly, but it can be extended by subclasses. This enforces the design intent that `Shape` serves as a base class for specific shapes like `Circle` or `Rectangle`, while preventing the creation of a generic `Shape` object.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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