In Java, methods declared with which keyword cannot be overridden in a subclass?

Introduction / Context:
Java is an object-oriented language that supports inheritance and method overriding. Subclasses can override methods of their superclasses to provide specialized behavior. However, sometimes a class designer wants to prevent a method from being overridden to preserve invariants or implementation details. Java provides specific modifiers that control whether methods can be overridden.

Given Data / Assumptions:

• We are talking about Java instance or static methods declared in classes.
• The question asks which keyword makes a method non-overridable in subclasses.
• The options include transient, abstract, final, and super.
• We assume basic familiarity with Java access modifiers and method declarations.

Concept / Approach:
The final keyword in Java is used to indicate that something cannot be modified or extended. When applied to a method, final tells the compiler that subclasses are not allowed to provide their own implementation with the same signature. This ensures that the behavior of that method is fixed in the class where it is declared. Other keywords such as transient and abstract have entirely different purposes and do not prevent overriding.

Step-by-Step Solution:
Step 1: Recall that final can be applied to variables, methods, and classes in Java.Step 2: For methods, final means that the method implementation is complete and cannot be overridden by any subclass.Step 3: Check the other keywords: transient is used for fields in serialization, abstract is used to declare methods without a body that must be overridden, and super is a keyword used to refer to the superclass, not a modifier.Step 4: Since the question is about preventing overriding, the correct match is the final keyword.Step 5: Therefore, methods declared as final cannot be overridden in subclasses.

Verification / Alternative check:
Java compiler errors confirm this behavior: if a subclass attempts to provide a new implementation for a final method, the compiler issues an error stating that the method cannot be overridden. This is true regardless of whether the subclass is in the same package or in a different one. Documentation of final also explicitly mentions this non-overridable property.

Why Other Options Are Wrong:
Option A, transient, is used only on fields to indicate that they should not be serialized; it does not affect overriding. Option B, abstract, requires overriding because an abstract method has no implementation and must be implemented in a concrete subclass. Option D, super, is a keyword used inside method bodies to refer to superclass members and cannot be used as a modifier on methods.

Common Pitfalls:
Some learners confuse abstract and final as opposite extremes but forget that abstract means "must be overridden" while final means "must not be overridden". Another pitfall is thinking that private methods are overridden; in fact, private methods are not visible to subclasses and are effectively not candidates for overriding at all. The explicit tool for preventing overriding is the final keyword.

Final Answer:
Methods declared with the keyword final cannot be overridden in Java.