Interview Questions For Java Developer Fresher
Java Developer Interview Questions for Freshers
As an aspiring Java developer, you may be asked various technical and non-technical questions during the interview process. Technical questions will likely cover your understanding of core Java concepts, data structures, algorithms, and object-oriented programming principles. Non-technical questions may focus on your problem-solving skills, teamwork abilities, and your motivation for pursuing a career in Java development. It's important to prepare for these questions and showcase your knowledge and enthusiasm for Java development to impress the interviewer and increase your chances of securing the job.
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1 - What is Java?
Java is a high-level, object-oriented programming language used for developing applications, mobile apps, and web programs. It is popular for its platform independence, meaning it can run on any operating system.
2) What is the differebetween JDK, JRE, and JVM?
JDK stands for Java Development Kit and is used for developing Java applications. It includes tools such as a compiler, debugger, and other necessary components. JRE stands for Java Runtime Environment and is used for executing Java programs. It includes JVM, class libraries, and other supporting files. JVM stands for Java Virtual Machine and is responsible for executing Java programs by converting bytecode into machine-specific code.
3) What is the difference between an interface and an abstract class?
An interface can only have abstract methods and cannot contain any implementation, while an abstract class can have both abstract and non-abstract methods. Additionally, a class can implement multiple interfaces, but can only extend one abstract class.
4) What is the difference between a constructor and a method?
A constructor is a special method that is used to initialize an object when it is created, whereas a method is used to perform any specific task or operation.
5) What is the importance of the main() method in Java?
The main() method is the entry point of a Java program and is required for the execution of the program. It is responsible for starting the execution of the program and can also pass command-line arguments to the program.
6) What is the difference between a local variable and an instance variable?
A local variable is declared and used within a method or a block of code, and its scope is limited to that particular method or block. An instance variable is declared within a class and is accessible to all methods within the class.
7) What is a package in Java?
A package is a collection of related classes and interfaces that provide a namespace to avoid naming conflicts in larger projects. It also helps in organizing and managing classes in a logical manner.
8) What is the difference between an array and an ArrayList?
An array is a fixed-size data structure that can hold elements of the same data type, whereas an ArrayList is a dynamic data structure that can hold elements of different data types and can grow or shrink dynamically.
9) What is method overloading?
Method overloading is the practice of having multiple methods with the same name but with different parameters. The compiler chooses the appropriate method based on the arguments passed to it.
10) What is method overriding?
Method overriding is the practice of redefining a method in the child class with the same name and signature as the method in the parent class. It allows the child class to provide its own implementation of the method.
11) What is a thread in Java?
A thread is a lightweight process that allows multiple tasks to be performed simultaneously within a single program. Threads can be created by extending the Thread class or implementing the Runnable interface.
12) What is the difference between a static and non-static method?
A static method belongs to the class and can be invoked without creating an instance of the class. A non-static method belongs to a particular object and can only be invoked through an instance of the class.
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13) What is an exception in Java?
An exception is an unexpected or unwanted event that disrupts the normal flow of a program. In Java, exceptions are objects that are used to handle these errors and maintain the program's integrity.
14) What is the difference between a checked and an unchecked exception?
A checked exception is an exception that is checked at compile-time and must be handled with a try-catch block. An unchecked exception is an exception that does not need to be checked at compile-time and can be handled at runtime.
15) What is inheritance in Java?
Inheritance is a mechanism of reusing code by creating a new class (child class) from an existing class (parent class). The child class inherits all the properties and methods of the parent class and can add its own unique features.
16) What is a constructor chaining?
Constructor chaining is the process of calling one constructor from another constructor within the same class. This allows for code reuse and helps in avoiding duplicate code in different constructors.
17) What is a marker interface?
A marker interface is an interface with no methods or constants, and it simply serves as a tag or marker for classes implementing it. Some commonly used marker interfaces in Java are Serializable and Cloneable.
18) What is a lambda expression?
A lambda expression is a concise way of representing an anonymous function. It does not have a name, and it can be passed around as a variable or a method parameter.
19) What is a try-with-resources statement?
A try-with-resources statement is used for automatically closing any resources that are declared inside the parentheses after the keyword “try.” It is useful for managing resources such as database connections or input/output streams.
20) What is polymorphism in Java?
Polymorphism refers to the ability of an object to take on different forms. In Java, this is achieved through method overriding and method overloading. This allows for a single method to perform different tasks based on the object's type.
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