Top 21 Coffee Concluding Modifier (Keyword) Interview Questions Together With Answers
The lastly modifier is ane of the of import keywords inwards Java. You tin give notice purpose this amongst a class, method, together with variable every bit well. Influenza A virus subtype H5N1 proficient cognition of lastly keyword is non solely essential for writing good, performant together with secure Java programs but besides to clear whatever Java interview. Interviewer pays exceptional attending to lastly keyword together with expects candidates knows how together with when to purpose the lastly modifier amongst variables, methods, together with classes. In this article, I lead keep collected Java interview questions which are based upon the concept of lastly modifier. You mightiness lead keep seen many of these questions on both telephonic together with face-to-face round. You tin give notice purpose this collection non solely to depository fiscal establishment tally your cognition most lastly keyword but besides to hit for lastly modifier from Java interview's perspective. If you lot lead keep come upwardly across whatever interesting lastly modifier inquiry which is non inwards this list, delight part amongst us every bit a comment together with I'll add together into this list.
1) What is the purpose of the lastly keyword inwards Java?
The lastly keyword tin give notice live used amongst a class, method, together with variables. If it is used amongst degree thence it prevents inheritance past times non allowing you lot to hit subclasses. If it is used amongst methods thence it prevents overriding, you lot cannot override a lastly method inwards Java. If it is used amongst variables thence they are treated every bit constant because you lot cannot alter their value in ane trial assigned. See here to larn to a greater extent than most lastly modifier inwards Java.
2) Can nosotros brand a variable lastly inwards Java? What is unlike betwixt a normal variable together with lastly variable?
Yes, you lot tin give notice brand a variable lastly inwards Java. The divergence betwixt normal variable together with lastly variable comes from multiple assignments. you lot tin give notice re-assign value to a normal variable but you lot cannot alter the value of a lastly variable in ane trial assigned. See here to larn to a greater extent than most when to brand a variable lastly inwards Java.
3) Can nosotros brand a method lastly inwards Java? explicate the divergence betwixt normal method together with lastly method
Yes, you lot tin give notice brand a method lastly inwards Java. The divergence is inwards the fact that you lot tin give notice override a non-final method, provided it'st non private together with static but you lot cannot override a lastly method inwards Java. See here to larn to a greater extent than most when to brand a method lastly inwards Java.
4) Can nosotros brand local variable lastly inwards Java?
Yes, you lot tin give notice brand local variable lastly inwards Java. In fact, this was mandatory, if you lot desire to access the local variable within an Anonymous degree until Java 8. From Java 8 onward, you lot don't ask to acquire far lastly but brand certain you lot don't alter the value in ane trial assigned. This is besides known every bit an effectively lastly variable inwards Java. See Java SE 8 for Really Impatient past times Cay S. Horstmann to larn to a greater extent than most the effectively lastly variable inwards Java.
5) What is a blank lastly plain or variable inwards Java?
Java allows you lot to hit a lastly fellow member variable without assignment but requires you lot to assign the value inwards either static initializer block, if fellow member variable is static or within every constructor, if fellow member variable is non-static. The lastly variable without assignment or value is called blank lastly variable, the compiler volition ensure that this plain is initialized inwards every path of execution. See here to larn to a greater extent than most the blank lastly variable inwards Java.
6) Can you lot alter the dry reason of the object to which a lastly reference variable is pointing?
Yes, you lot tin give notice alter the dry reason of the object referred past times a lastly variable. This is ane of the tricky concept inwards Java together with oftentimes displace subtle errors. One of the most mutual examples of this is Collection classes e.g. ArrayList or HashMap referenced past times a lastly variable. You tin give notice notwithstanding add, take together with update elements but you lot cannot alter the lastly variable to signal to around other collection. This is unlike thence immutable or read-only collection inwards Java, where you lot cannot perform whatever add, take or update functioning in ane trial created.
7) Can nosotros brand an array lastly inwards Java? Can you lot alter its elements?
Yes, you lot tin give notice brand an array lastly inwards Java together with you lot tin give notice alter it's elements every bit well. This is genuinely the follow-up to the previous question, both array together with collection classes tin give notice live made lastly together with you lot tin give notice notwithstanding alter their elements.
8) Can you lot brand a Collection lastly inwards Java e.g. ArrayList? What is the impact?
Yes, you lot tin give notice brand a Collection lastly inwards Java. The touching is cypher but the lastly variable cannot live swapped amongst around other Collection, but you lot tin give notice notwithstanding add, take together with update elements inwards ArrayList or whatever collection classes. This is over again related to previous 2 questions. See Big Java: Early Objects to larn to a greater extent than most this concept.
9) What is the divergence betwixt abstract method together with lastly method inwards Java?
The abstract method is incomplete patch the lastly method is regarded every bit complete. The solely way to purpose an abstract method is past times overriding it, but you lot cannot override a lastly method inwards Java. You should besides yell upwardly that a method cannot live both abstract together with lastly inwards Java because both are contrary to each other.
10) What is the purpose of lastly degree inwards Java?
You brand a degree lastly when you lot think it's consummate together with nobody should alter the characteristic past times creating a subclass. Generally, security sensitive classes are made lastly inwards Java e.g. String. Another argue is performance, compiler, together with JIT both tin give notice brand a lot of supposition if a degree is lastly because they know overriding or polymorphism volition non come upwardly into the picture.
11) Can you lot overload a lastly method inwards Java?
Yes, you lot tin give notice overload a lastly method inwards Java, yell upwardly overloading is unlike than overriding together with you lot solely ask to declare the method amongst the same mention inwards the same degree but unlike method signature for overloading. See rules of method overloading to larn to a greater extent than most overloading inwards Java.
12) Can you lot override a lastly method inwards Java?
No, you lot cannot override a lastly inwards Java. You brand a method lastly inwards Java to forbid overriding, thence no inquiry of farther allowing overriding.
13) Can nosotros brand a static method lastly inwards Java?
Yes, you lot tin give notice brand a static method lastly inwards Java, cypher prevents you lot making a static method from beingness a lastly ane every bit well. In fact, they both acquire manus inwards hand.
14) Can nosotros brand an abstract method lastly inwards Java?
No, you lot cannot brand an abstract method lastly inwards Java because, inwards guild to purpose an abstract method, you lot must override it but the lastly method cannot live overridden inwards Java. The compiler volition flag an error if you lot purpose both abstract together with final keyword together amongst degree or method inwards Java. See Core Java Volume 1 - Fundamentals to larn to a greater extent than most rules of Java programming.
15) Can nosotros purpose non-final local variables within an Anonymous class?
Yes together with No, it's non allowed until Java 7, from Java 8 onward you lot tin give notice purpose a non-final local variable within an anonymous or local inner class, provided it's effectively final, which way it's non changed afterwards initialized. See here to larn to a greater extent than most the effectively lastly concept inwards Java 8.
16) Can you lot declare Constructor every bit lastly inwards Java?
No, Constructors cannot live made lastly inwards Java. The compiler volition throw an error if you lot endeavor to brand a constructor lastly inwards Java. See here to larn to a greater extent than most constructor inwards Java.
17) What is constant inwards Java?
Influenza A virus subtype H5N1 static lastly variable is known every bit constant inwards Java. They are besides known every bit a compile fourth dimension constant because of their value at the fourth dimension of compilation. They are besides inlined at the customer end, way if you lot are using a static final variable thence its value volition live copied to your degree at compile time. Which besides way that you lot ask to recompile all the classes which purpose the static lastly variable, whenever you lot alter the value of a static lastly field. This has the potential to hit subtle bugs. Read Java Coding Guidelines to avoid such mistakes.
18) Are static lastly variables are thread-safe?
There are 2 types of static lastly variables, primitive, together with reference. Initialization of all static lastly variables is thread security because it's done inwards static initializer block. Similarly primitive static lastly variable is besides thread-safe because you lot cannot modify their value in ane trial created, but reference static lastly variable may or may non live thread-safe. If the object to which your lastly variable is referring is Immutable or thread-safe thence it is otherwise not.
19) Can a degree live abstract together with lastly at the same time?
No, it's non possible because the solely way to purpose abstract degree is past times extending it together with creating a concrete subclass, patch it's non possible to extend a lastly degree inwards Java.
20) When to brand a method lastly inwards Java?
You brand a method lastly when you lot know that it's consummate together with you lot desire to ensure that it should non live overridden. One of the examples of a lastly method is template methods from Template blueprint pattern, which outlines the algorithm. That method should live lastly thence that sub-classes cannot alter the algorithm, they are solely allowed to customize private steps which are represented past times abstract method.
21) When to brand a degree lastly inwards Java?
You brand a degree lastly when you lot don't desire anyone should extend it. This is mainly done due to security argue because it besides hampers extensibility of your program. Influenza A virus subtype H5N1 span of examples of lastly classes inwards JDK is String, Integer, together with other wrapper class. See here to larn to a greater extent than most why String degree is made lastly inwards Java.
21 Java lastly modifier Interview Questions
So, what are nosotros waiting for? let's start amongst the starting fourth dimension inquiry inwards this list:1) What is the purpose of the lastly keyword inwards Java?
The lastly keyword tin give notice live used amongst a class, method, together with variables. If it is used amongst degree thence it prevents inheritance past times non allowing you lot to hit subclasses. If it is used amongst methods thence it prevents overriding, you lot cannot override a lastly method inwards Java. If it is used amongst variables thence they are treated every bit constant because you lot cannot alter their value in ane trial assigned. See here to larn to a greater extent than most lastly modifier inwards Java.
2) Can nosotros brand a variable lastly inwards Java? What is unlike betwixt a normal variable together with lastly variable?
Yes, you lot tin give notice brand a variable lastly inwards Java. The divergence betwixt normal variable together with lastly variable comes from multiple assignments. you lot tin give notice re-assign value to a normal variable but you lot cannot alter the value of a lastly variable in ane trial assigned. See here to larn to a greater extent than most when to brand a variable lastly inwards Java.
3) Can nosotros brand a method lastly inwards Java? explicate the divergence betwixt normal method together with lastly method
Yes, you lot tin give notice brand a method lastly inwards Java. The divergence is inwards the fact that you lot tin give notice override a non-final method, provided it'st non private together with static but you lot cannot override a lastly method inwards Java. See here to larn to a greater extent than most when to brand a method lastly inwards Java.
4) Can nosotros brand local variable lastly inwards Java?
Yes, you lot tin give notice brand local variable lastly inwards Java. In fact, this was mandatory, if you lot desire to access the local variable within an Anonymous degree until Java 8. From Java 8 onward, you lot don't ask to acquire far lastly but brand certain you lot don't alter the value in ane trial assigned. This is besides known every bit an effectively lastly variable inwards Java. See Java SE 8 for Really Impatient past times Cay S. Horstmann to larn to a greater extent than most the effectively lastly variable inwards Java.
5) What is a blank lastly plain or variable inwards Java?
Java allows you lot to hit a lastly fellow member variable without assignment but requires you lot to assign the value inwards either static initializer block, if fellow member variable is static or within every constructor, if fellow member variable is non-static. The lastly variable without assignment or value is called blank lastly variable, the compiler volition ensure that this plain is initialized inwards every path of execution. See here to larn to a greater extent than most the blank lastly variable inwards Java.
6) Can you lot alter the dry reason of the object to which a lastly reference variable is pointing?
Yes, you lot tin give notice alter the dry reason of the object referred past times a lastly variable. This is ane of the tricky concept inwards Java together with oftentimes displace subtle errors. One of the most mutual examples of this is Collection classes e.g. ArrayList or HashMap referenced past times a lastly variable. You tin give notice notwithstanding add, take together with update elements but you lot cannot alter the lastly variable to signal to around other collection. This is unlike thence immutable or read-only collection inwards Java, where you lot cannot perform whatever add, take or update functioning in ane trial created.
7) Can nosotros brand an array lastly inwards Java? Can you lot alter its elements?
Yes, you lot tin give notice brand an array lastly inwards Java together with you lot tin give notice alter it's elements every bit well. This is genuinely the follow-up to the previous question, both array together with collection classes tin give notice live made lastly together with you lot tin give notice notwithstanding alter their elements.
8) Can you lot brand a Collection lastly inwards Java e.g. ArrayList? What is the impact?
Yes, you lot tin give notice brand a Collection lastly inwards Java. The touching is cypher but the lastly variable cannot live swapped amongst around other Collection, but you lot tin give notice notwithstanding add, take together with update elements inwards ArrayList or whatever collection classes. This is over again related to previous 2 questions. See Big Java: Early Objects to larn to a greater extent than most this concept.
9) What is the divergence betwixt abstract method together with lastly method inwards Java?
The abstract method is incomplete patch the lastly method is regarded every bit complete. The solely way to purpose an abstract method is past times overriding it, but you lot cannot override a lastly method inwards Java. You should besides yell upwardly that a method cannot live both abstract together with lastly inwards Java because both are contrary to each other.
10) What is the purpose of lastly degree inwards Java?
You brand a degree lastly when you lot think it's consummate together with nobody should alter the characteristic past times creating a subclass. Generally, security sensitive classes are made lastly inwards Java e.g. String. Another argue is performance, compiler, together with JIT both tin give notice brand a lot of supposition if a degree is lastly because they know overriding or polymorphism volition non come upwardly into the picture.
11) Can you lot overload a lastly method inwards Java?
Yes, you lot tin give notice overload a lastly method inwards Java, yell upwardly overloading is unlike than overriding together with you lot solely ask to declare the method amongst the same mention inwards the same degree but unlike method signature for overloading. See rules of method overloading to larn to a greater extent than most overloading inwards Java.
12) Can you lot override a lastly method inwards Java?
No, you lot cannot override a lastly inwards Java. You brand a method lastly inwards Java to forbid overriding, thence no inquiry of farther allowing overriding.
13) Can nosotros brand a static method lastly inwards Java?
Yes, you lot tin give notice brand a static method lastly inwards Java, cypher prevents you lot making a static method from beingness a lastly ane every bit well. In fact, they both acquire manus inwards hand.
14) Can nosotros brand an abstract method lastly inwards Java?
No, you lot cannot brand an abstract method lastly inwards Java because, inwards guild to purpose an abstract method, you lot must override it but the lastly method cannot live overridden inwards Java. The compiler volition flag an error if you lot purpose both abstract together with final keyword together amongst degree or method inwards Java. See Core Java Volume 1 - Fundamentals to larn to a greater extent than most rules of Java programming.
15) Can nosotros purpose non-final local variables within an Anonymous class?
Yes together with No, it's non allowed until Java 7, from Java 8 onward you lot tin give notice purpose a non-final local variable within an anonymous or local inner class, provided it's effectively final, which way it's non changed afterwards initialized. See here to larn to a greater extent than most the effectively lastly concept inwards Java 8.
16) Can you lot declare Constructor every bit lastly inwards Java?
No, Constructors cannot live made lastly inwards Java. The compiler volition throw an error if you lot endeavor to brand a constructor lastly inwards Java. See here to larn to a greater extent than most constructor inwards Java.
17) What is constant inwards Java?
Influenza A virus subtype H5N1 static lastly variable is known every bit constant inwards Java. They are besides known every bit a compile fourth dimension constant because of their value at the fourth dimension of compilation. They are besides inlined at the customer end, way if you lot are using a static final variable thence its value volition live copied to your degree at compile time. Which besides way that you lot ask to recompile all the classes which purpose the static lastly variable, whenever you lot alter the value of a static lastly field. This has the potential to hit subtle bugs. Read Java Coding Guidelines to avoid such mistakes.
18) Are static lastly variables are thread-safe?
There are 2 types of static lastly variables, primitive, together with reference. Initialization of all static lastly variables is thread security because it's done inwards static initializer block. Similarly primitive static lastly variable is besides thread-safe because you lot cannot modify their value in ane trial created, but reference static lastly variable may or may non live thread-safe. If the object to which your lastly variable is referring is Immutable or thread-safe thence it is otherwise not.
19) Can a degree live abstract together with lastly at the same time?
No, it's non possible because the solely way to purpose abstract degree is past times extending it together with creating a concrete subclass, patch it's non possible to extend a lastly degree inwards Java.
20) When to brand a method lastly inwards Java?
You brand a method lastly when you lot know that it's consummate together with you lot desire to ensure that it should non live overridden. One of the examples of a lastly method is template methods from Template blueprint pattern, which outlines the algorithm. That method should live lastly thence that sub-classes cannot alter the algorithm, they are solely allowed to customize private steps which are represented past times abstract method.
21) When to brand a degree lastly inwards Java?
You brand a degree lastly when you lot don't desire anyone should extend it. This is mainly done due to security argue because it besides hampers extensibility of your program. Influenza A virus subtype H5N1 span of examples of lastly classes inwards JDK is String, Integer, together with other wrapper class. See here to larn to a greater extent than most why String degree is made lastly inwards Java.
That's all inwards this listing of Java Interview questions based upon the lastly keyword. We lead keep covered lastly variable, methods, together with lastly classes. We besides lead keep a span of inquiry on the human relationship of lastly modifier amongst Java concurrency.
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