Which of the following statements is/are correct regarding the programming of JAVA? I. A class that is marked as final cannot be overwritten. II. A method that is marked as final cannot be overridden.
Both I and II
Understanding the Java final Keyword
In Java programming, the final keyword is a non-access modifier that can be applied to classes, methods, and variables. When used, it restricts the modification or inheritance of the element it is applied to.
Analysis of Statement I: Final Classes
Statement I says: "A class that is marked as final cannot be overwritten."
In Java, when a class is declared with the final keyword, it means that this class cannot be extended or inherited by any other class. Inheritance allows a subclass to inherit properties and behaviors from a superclass. By marking a class as final, the designer prevents this. While the term "overwritten" isn't the standard terminology for classes (inheritance is the concept), the intent of the statement aligns with the rule: a final class cannot be inherited, thus its definition cannot be altered or built upon by creating a subclass.
Examples of final classes in the Java API include String, Integer, and other wrapper classes. This is often done for security or immutability reasons.
Therefore, Statement I is correct in principle, as a final class cannot be inherited.
Analysis of Statement II: Final Methods
Statement II says: "A method that is marked as final cannot be overridden."
Method overriding is a concept in object-oriented programming where a subclass provides a specific implementation for a method that is already provided by its superclass. When a method in a superclass is declared with the final keyword, it signifies that this specific implementation of the method cannot be changed or overridden by any subclass.
If a subclass tries to define a method with the same signature as a final method in its superclass, the Java compiler will report an error.
Therefore, Statement II is correct.
Conclusion
Based on the analysis of both statements concerning the final keyword in Java programming:
- A class marked as final cannot be inherited (preventing it from being "overwritten" in the sense of extension).
- A method marked as final cannot be overridden by a subclass.
Both statements accurately describe the restrictions imposed by the final keyword in Java.
| Applied To | Effect | Description |
|---|---|---|
| Variable | Value cannot be changed after initialization | Creates a constant. For reference types, the reference cannot be changed, but the object content might be mutable unless the object itself is immutable. |
| Method | Cannot be overridden by subclasses | Ensures that the method's implementation remains consistent across all subclasses. |
| Class | Cannot be inherited by subclasses | Prevents further extension of the class, often used for security or immutability. |
Revision Table: Key Concepts of Java final
- final classes prevent inheritance.
- final methods prevent overriding.
- final variables become constants.
Additional Information: Java Modifiers
The final keyword is one of several modifiers in Java that control access and behavior. Other common modifiers include:
- Access Modifiers: public, private, protected, default (package-private). These control the visibility of classes, variables, methods, and constructors.
- Non-Access Modifiers: Apart from final, these include static, abstract, synchronized, volatile, transient, and native. Each has a specific purpose in defining the behavior or characteristics of the element it modifies.
Understanding how modifiers like final work is crucial for writing correct and robust Java code, especially when dealing with inheritance and method overriding.
Important Questions from Java
When an applet begins, which of the following sequence methods is CORRECT?
1) start()
2) paint()
3) init()
What will be the output of the following Java program?
class test
{public static void main (String args [ ])
{
System.out.println(20 + 30 + "Java");
System.out.println("Java" + 20 + 30);
}
}
In Java, the 'PreparedStatement' interface is a sub interface which is used to execute __________ query.
Which of the following is NOT a java primitive type?
Which of the following is/are the rules to declare variables in Java?
