What’s Java?
Java is a high-level programming language that was developed by James Gosling in the year 1982. It’s grounded on the principles of object-acquainted programming and can be used to develop large-scale applications.
The backing article will cover all the popular Core Java interview questions,
- String Handling interview questions,
- Java 8 interview questions,
- Java multithreading interview questions,
- Java OOPs interview questions,
- Java exception handling interview questions
- collections interview questions, and some constantly asked Java rendering interview questions.
Go through all the important questions to magnify your chances of performing well in the Java Interviews. The questions will revolve around the introductory, core & advanced fundamentals of Java.
Java Interview Questions for Freshers
1. Why is Java a platform-independent language?
Java language was developed so that it doesn’t depend on any hardware or software because the compiler compiles the code and also converts it to platform-independent byte code which can be run on multiple systems.
2. Why is Java not a pure object-acquainted language?
Java supports primitive data types- byte, boolean, char, short, int, float, long, and double and hence it isn’t a pure object-acquainted language.
3. Difference between Heap and Stack Memory in Java. And how Java utilizes this.
Stack memory is the portion of memory that was assigned to every individual program. And it was fixed. On the other hand, Heap memory is the portion that wasn’t allocated to the Java program but it’ll be available for use by the Java program when it’s needed, substantially during the runtime of the program.
Java Utilizes this memory as When we write a Java program also all the variables, styles, etc are stored in the stack memory. When we produce any object in the Java program also that object is created in the heap memory. And it was substantiated by the stack memory.
4. What’s a Class in Java?
A class is a blueprint for objects. It defines a datatype by speeding data and methods that work on the data into one single unit.
5. What’s an Object in Java?
An object is an example of a class. It has a state and geste, represented by fields( variables) and methods, independently.
6. What are Constructors in Java?
Constructors are special methods that are called when an object is expressed. They have the same name as the class and don’t have a return type.
7. Can Java be said to be the complete object-acquainted programming language?
It isn’t wrong if we claim that Java is the complete object-acquainted programming language because everything in Java is under the classes and we can pierce them by creating the objects. But we can indeed say that Java isn’t a fully object-acquainted programming language because it has the support of primitive data types like int, float, char, boolean, double, etc. Now for the question Is Java a fully object-acquainted programming language? We can say that- Java isn’t a pure object-acquainted programming language, because it has direct access to primitive data types. And these primitive data types do not directly belong to the Integer classes.
8. How is Java different from C++?
C++ is only a collected language, whereas Java is a collected as well as an interpreted language.
Java programs are machine-independent whereas a C++ program can run only in the machine in which it’s collected.
C++ allows users to use pointers in the program. In comparison, Java doesn’t allow it. Java internally uses pointers.
C++ supports the concept of Multiple inheritances whereas Java does not support this. And it’s due to avoiding the complexity of name ambiguity that causes the diamond problem.
9. Explain the four main OOP conceptions.
- Encapsulation: Wrapping the data( variables) and law( styles) together as a single unit.
- Heritage: A medium where one class inherits the properties and behavior( styles) of another class.
- Polymorphism: The capability of a, changing function, or object to take multiple forms. It includes method overloading and method booting.
- Abstraction: Hiding the complex perpetration details and showing only the essential features of the object.
10. What’s heritage?
Heritage is a medium where a new class( class/ child class) inherits parcels and geste
from a being class( superclass/ parent class).
11. What are the default values assigned to variables and instances in Java?
There are no default values set to the variables in Java. We need to initialize the value before using it. else, it’ll throw a compendium error of( Variable might not be initialized).
- But for instance, if we produce the object, also the default value will be initialized by the default constructor depending on the data type. . . still, it’ll also be assigned to null If it’s a reference.
- still, it’ll also assign to 0 If it’s numeric.
- still, also it’ll be assigned to false If it’s a boolean. Etc.
12. What do you mean by data encapsulation?
- Data Encapsulation is an Object-acquainted Programming conception of hiding the data attributes and their behaviors in a single unit.
- It helps inventors follow modularity while developing software by ensuring that each object is independent of other objects by having its methods, attributes, and functionalities.
- It’s used for the security of the private properties of an object and hence serves the purpose of data hiding.
13. Can you tell the difference between the equals() method and the equivalency operator (==) in Java?
We’re formerly apprehensive of the (==) equals operator. We’ve used this to compare the equivalency of the values. But when we talk about the terms of object-acquainted programming, we deal with the values in the form of objects. This object may carry multiple types of data. So using the (==) operator doesn’t work in this case. So we need to go with the. equals() method.
Both( (==) and. equals()) primary functionalities are to contrast the values, but the secondary functionality is different.
So to understand this better, let’s consider this with the example-
String str1 = ” InterviewBit”;
String str2 = ” InterviewBit”;
system. out.printin'( str1 == str2);
This code will publish true. We know that both strings are equals so it’ll publish true. But then (==) Operators don’t compare each character in this case. It compares the memory location. And because the string uses the constant pool to save the values in the memory, both str1 and str2 are stored at the same memory location.
14. Compactly explain the concept of constructor overloading
Constructor overloading is the process of creating multiple constructors in the class conforming to the same name with a difference in the constructor parameters. Depending upon the number of parameters and their corresponding types, distinguishing of the different types of constructors is done by the compiler.
15. A single try block and multiple catch blocks can co-occur in a Java Program. Explain.
Yes, multiple catch blocks can live but specific approaches should come prior to the general approach because only the first catch block satisfying the catch condition is executed.
16. Explain the use of the final keyword in variable, method, and class.
In Java, the final keyword is used to define something as constant/ final and represents the access modifier.
- final variable
When a variable is announced as final in Java, the value can’t be modified once it has been assigned. still, also it can be assigned only by the constructor of the class If any value has not been assigned to that variable.
- final method
A method declared as final can not be hoofed by its children’s classes. A constructor can not be marked as final because whenever a class is inherited, the constructors aren’t inherited. Hence, marking it final does not make sense. Java throws a compilation error saying-
- final class No classes can be inherited from the class declared as final. But that final class can extend other classes for its use.
17. What’s a Java Exception?
An exception is an event that disrupts the normal flow of the program. It’s an object that represents an error or an unanticipated event that occurs during the commission of a program.
18. What are the kinds of exceptions in Java?
- Checked Exceptions Exceptions that are checked at collect- time(e.g., IOException, SQLException).
- Unchecked Exceptions Exceptions that are checked at runtime(e.g., NullPointerException, ArrayIndexOutOfBoundsException).
- Errors Serious problems that a reasonable application shouldn’t try to catch(e.g., OutOfMemoryError, StackOverflowError).
19. What’s the difference between abstract class and affiliate?
- Abstract Class: A class that can not be expressed and may contain abstract methods( methods without a body) as well as concrete methods( methods with a body). A class can extend only one philosophical class.
- Interface: A reference type in Java, analogous to a class, that can contain only abstract methods( until Java 8, which introduced dereliction and static methods). A class can apply multiple interfaces.
20. What’s a Java Stream?
A stream is a sequence of elements that supports colorful methods to perform operations on the elements. Streams can be used to reuse collections of objects. They give an ultramodern, functional approach to handling collections and data processing.
Conclusion
Preparing for a Java interview involves understanding both introductory and advanced concepts. Familiarizing yourself with these common questions and their answers can help you gain confidence and perform well in your interview. Good luck!
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