Java Full Stack Developer Interview Questions
Top Java Full Stack Developer Interview Questions
Java full stack developer interview questions cover a wide range of topics, from core Java concepts to front-end development and database management. Candidates may be asked about their experience with server-side frameworks like Spring and Hibernate, their knowledge of front-end technologies like HTML, CSS, and JavaScript, and their ability to work with databases using SQL. Employers may also ask about problem-solving skills, project experience, and coding proficiency. Overall, the interview aims to assess a candidate's understanding of the full software development stack and their ability to work with a variety of technologies to create robust and efficient applications.
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1 - What is the difference between Java Native Interface (JNI) and Java Native Access (JNA)?
JNI is a standard programming interface that allows Java programs to interact with native code written in programming languages such as C and C++. JNA is a more modern, lightweight alternative to JNI, allowing Java programs to interact with native code without the need for a separate library. JNA is also easier to use and avoids some of the performance overhead associated with JNI.
2) What is inheritance in Java?
Inheritance is a concept in object-oriented programming that allows a new class to be based on an existing class. The new class, known as a subclass, inherits the attributes and methods of the existing class, known as the superclass. This allows for reusability of code and facilitates the creation of more complex class structures.
3) Explain the difference between an abstract class and an interface.
An abstract class is a special kind of class in Java that cannot be instantiated. It contains one or more abstract methods, which are methods without an implementation. An interface, on the other hand, is a collection of abstract methods and/or constants. A class can implement multiple interfaces but can only inherit from one abstract class.
4) How does garbage collection work in Java?
Garbage collection is an automatic process in Java that reclaims memory from objects that are no longer referenced by the program. When an object is no longer referenced, it is marked as eligible for garbage collection. The garbage collector then runs in the background, freeing up memory by destroying these unused objects.
5) What is a Java Virtual Machine (JVM)?
A Java Virtual Machine (JVM) is a software implementation that runs Java bytecode. It acts as a virtual machine and translates Java bytecode into machine-specific code, allowing Java programs to be executed on any platform.
6) What is the difference between a compiler and an interpreter?
A compiler translates source code into machine code before it is executed. An interpreter, on the other hand, reads and executes the source code line by line, without translating it into machine code. Java is both compiled and interpreted – it is first compiled into bytecode and then interpreted by the JVM.
7) What is the purpose of the ‘static’ keyword in Java?
The ‘static’ keyword is used to create a class-level variable or method that can be accessed without creating an instance of the class. It can also be used to reference a static nested class, which is a class declared within another class and is accessed using the outer class.
8) What is the difference between a class variable and an instance variable?
Class variables, also known as static variables, are declared using the ‘static’ keyword and are shared across all instances of a class. Instance variables are declared within a class but outside of any method and are unique to each instance of the class.
9) What is polymorphism in Java?
Polymorphism is the ability of an object to take on multiple forms. In Java, this is achieved through method overloading and method overriding. Method overloading allows a class to have multiple methods with the same name but different parameters, while method overriding allows a subclass to override a method from its superclass.
10) What is the difference between a shallow copy and a deep copy in Java?
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A shallow copy copies the references of an object's fields, while a deep copy copies the actual values of an object's fields. This means that if the original object is modified, the shallow copy will also be affected, while the deep copy remains unchanged.
11) What is a class loader in Java?
A class loader is a part of the Java Runtime Environment (JRE) that loads classes into memory during runtime. It is responsible for locating and loading classes, interfaces, and various resources needed by a Java program.
12) What is the purpose of the ‘this’ keyword in Java?
The ‘this’ keyword is used to refer to the current instance of a class. It can be used within a class to access instance variables, methods, or constructors. It is particularly useful for differentiating between local variables and instance variables with the same name.
13) What are the access modifiers available in Java?
There are four access modifiers in Java: public, private, protected, and default. Public means a class, method, or variable can be accessed from any other class. Private restricts access to the declared class only. Protected allows access within the package and subclasses. Default, or package-private, allows access within the same package only.
14) What is a constructor in Java?
A constructor is a special method that is used to initialize objects of a class. It is called automatically when an object of a class is created and is used to set initial values for the object's member variables.
15) What is the difference between an ArrayList and a LinkedList in Java?
An ArrayList is a resizable array implementation, while a LinkedList is a doubly-linked list implementation. ArrayLists are good for random access and searching, while LinkedLists are good for adding or removing elements from the middle of the list. In general, ArrayLists are faster for most operations, except for adding or removing elements from the beginning or middle of the list.
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