In Java, how do you define an abstract class in code, and what syntax indicates that a class is abstract?

Introduction / Context:
Once you understand what an abstract class is, the next basic step is knowing how to declare one in Java source code. The syntax is simple but must be precise. This question asks you to identify the correct way to mark a class as abstract in Java.

Given Data / Assumptions:

• Java uses keywords to indicate special properties of classes, such as public, final, and abstract.
• An abstract class cannot be instantiated directly and may contain abstract methods.
• The question focuses on the correct syntax for declaring an abstract class, not its internal contents.

Concept / Approach:
In Java, the abstract keyword is placed before the class keyword in the class declaration to mark the class as abstract. You can combine abstract with other modifiers such as public or package private. The name of the class is independent of the abstract status; there is no requirement to use any naming convention like adding Abstract in the name. Without the abstract keyword, the class is considered concrete and must provide implementations for all inherited abstract methods.

Step-by-Step Solution:
Step 1: The minimal abstract class declaration looks like abstract class Shape { } which makes Shape an abstract class in the default package access.Step 2: You can also write public abstract class Shape { } to make the class public and abstract.Step 3: Inside this class, you may declare abstract methods such as public abstract void draw(); and concrete methods with bodies.Step 4: The key syntax marker is the abstract keyword before the class keyword, signaling to the compiler that this class cannot be instantiated.Step 5: Option A correctly shows this syntax by using public abstract class Shape { } as an example, so it is the correct answer.

Verification / Alternative check:
If you omit the abstract keyword and still declare abstract methods inside the class, the compiler reports an error insisting that the class must be abstract. After adding abstract to the class declaration, the error disappears. Trying to instantiate an abstract class with new Shape() generates a different compile time error, which confirms that the abstract keyword has taken effect.

Why Other Options Are Wrong:
Option B suggests that placing a class in a special package makes it abstract, which is not true; packages do not control whether a class is abstract. Option C uses a naming convention ShapeAbstract but does not use the abstract keyword, so the class would be considered concrete. Option D incorrectly claims that a class with only static methods becomes abstract automatically; Java does not apply such a rule.

Common Pitfalls:
Developers sometimes rely too heavily on naming conventions and forget that the compiler cares only about keywords, not names. Another pitfall is marking classes abstract when they could be interfaces or could be fully concrete, which may complicate testing. Always use the abstract keyword explicitly when you intend a class to be abstract and ensure that its design genuinely benefits from being uninstantiable and partially implemented.

Final Answer:
You define an abstract class in Java by placing the abstract keyword in the class declaration, for example public abstract class Shape { }.