Do you want to test your programming skills with Java Programming Language? Prepare for the interviews of top companies by checking your skill level through our Java Interview Questions and Answers.
Java is used widely in the IT industry for application development, game development, and mobile app development.
Top companies are hiring a large number of freshers and professionals to perform various roles in the Java domain.
Our “Java Interview Questions and Answers” will help candidates to clear the technical rounds successfully.
- How Java is a platform-independent language?
Java was developed in a way that does not require depending on any hardware or software as its compiler compiles the code and converts it to platform-independent byte code that can be executed on multiple systems.
The only condition is to run the byte code is for the machine to have a JRE (Java Runtime Environment) installed in it.
- What are the special features of the Java programming language?
Java is the programming language that can write once and run anywhere. It is a platform-independent programming language with the following features.
- Language Compatibility
- Java Native Interface to access libraries
- Automatic Garbage Collection
- Compiled and Interpreted Language
- Easy to learn with OOPs concepts
- Secured features to develop virus-free apps
- Java Virtual Machine and Java Runtime Environment
- Why do pointers are not utilized in Java Programming Language?
Pointers are complicated concepts to learn and implement moreover, it is unsafe to use by beginner programmers.
As Java focuses on code simplicity, the usage of pointers becomes challenging and it leads to potential errors.
Security is the issue when using pointers as it makes the way for hackers to access memory directly.
The usage of pointers will make the garbage collection procedure quite slow and erroneous. Instead of pointers, Java is using references as they can’t be manipulated easily.
- Define instance variable
Instance variables are variables that can be accessible by all the methods of the class and they are declared outside the methods and inside the class.
Instance variables describe the properties of an object and remain bound to it at any cost. All the objects of the class will have their copy of the variables.
If any modification is done on these variables the instance will be impacted by it. All other instances continue to remain unaffected.
Example:
class Employee
{
public String EmpName;
public double EmpSalary;
public int EmpAge;
}
- What is a local variable?
Local variables are the variables that are present within the block, function, or constructor that can be accessed only inside the respective class.
The utilization of these variables is restricted to the block scope. Whenever a local variable is declared inside a method, the other class methods will not know about the local variable.
Example:
public void Employee()
{
String EmpName;
double EmpSalary;
int EmpAge;
}
- Describe JIT compiler
JIT is the short form of Just-In-Time compiler used for improving the performance during run time.
It compiles the part of byte code that has similar functionality at the same time for reducing the amount of compilation time for the code to execute.
This is the translator of source code to convert into machine-executable code. It works as follows
- At first, the java source code (.java) was converted into byte code using the javac compiler
- Then, the .class files are loaded at runtime by JVM (Java Virtual Machine) using an interpreter for converting them to machine-understandable codes.
- JIT compiler is the part of JVM and when it is enabled, the JVM analyses the method class in the .class files and compiles them to get more efficient native code. It ensures that the prioritized method calls are optimized.
- Finally, the JVM executes the optimized code directly instead of interpreting the code again. Hence the performance and speed will be increased for the execution of codes.
- How can you declare an infinite loop in Java?
Infinite loops are the loops that run infinitely without breaking conditions Examples are as follows
Using For Loop:
for (; 😉
{
//Business Logic
//Any Break Logic
}
Using While Loop:
while (true)
{
//Business Logic
//Any Break Logic
}
Using Do-While Loop:
do
{
//Business Logic
//Any Break Logic
} while (true);
- What is constructor overloading?
Constructor overloading is the important process of Java to create multiple constructors in the class that contains the same name with different types of constructor parameters.
Different types of constructors are done by the compiler depending upon the number of parameters and their corresponding types.
Below is the example.
class Employee
{
int variable1, variable2;
double variable3;
public Employee (int development, int testing)
{
variable1 = development;
variable2 = testing;
}
public Employee (int development)
{
variable1 = development;
}
public Employee (double salaries)
{
variable3 = salaries;
}
}
There are three constructors in the above example and all three have differed based on their parameter types and their numbers.
- Define Method Overloading
Method overloading is the process of handling different methods in the same class that consists of the same name.
All the functions will differ in the number or type of parameters. It takes place inside a class and enhances program readability.
The major difference in the return type of the method will not promote method overloading. An example of the method overloading is below
class OverloadingHelp
{
public int findarea (int l, int b)
{
int var1;
var1 = l * b;
return var1;
}
public int findarea (int l, int b, int h)
{
int var2;
var2 = l * b * h;
return var2;
}
}
In the above example, both functions have the same name but they are differing in the number of arguments.
When the first method calculates the area of the rectangle, the second method calculates the area of the cuboid.
- What is Method Overriding?
Method overriding is the concept that two methods have the same name that presents in two different classes in which an inheritance relationship is present.
It is possible for the derived class to use the particular method of the parent class using method overriding. Below is the example.
class Animal
{
public int run (int distance, int time)
{
int speed = distance / time;
return speed;
}
}
class SeaAnimal extends Animal
{
public int run (int distance, int time)
{
int speed = distance / time;
speed = speed * 2;
return speed;
}
}
In the above example, both class methods have the name run with the same parameters namely distance and time.
If the derived class method is called when the base class method run gets overridden by the parameters and functions of the derived class.
- What is the use of the final keyword in variable, method, and class?
The final keyword in the Java programming language is used to define something as constant or final and represents the non-access modifier.
Final Variable: The value can’t be modified once it has been assigned when a variable is declared as final in the Java program.
If any value has not been assigned to that variable, then it will be assigned only by the constructor of the class.
Final Method: When the method is declared as final, then it can’t be overridden by the derived classes.
A constructor can’t be marked as final as whenever a class is inherited, the constructor is not inherited.
So, declaring it as final is meaningless. Java throws compilation error saying – ‘modifier final not allowed here.
Final Class: No classes can be inherited from the class that is declared as final. But the final class can derive other classes for its usage.
- Why should you use generics in Java Programming?
Compile-time type safety is offered by using generics. It allows users to catch unnecessary invalid types at compile time.
Generic methods and classes help programmers specify a single method declaration, a set of related methods, or related types with an available class declaration.
- What are the various directives in JSP?
Directives are the instructions processed by JSP (Java Server Page) Engine.
After the JSP is compiled into a Servlet, Directives set page-level instructions, insert external files, and define customized tag libraries.
Directives are defined using the symbols that start with “<%@ and then end with “%>”
Following are the various types of directives
- Include directive: It includes a file and combines the content of the whole file with currently active pages.
- Page directive: It defines particular attributes in the JSP like the buffer and error page
- Taglib: It declares a custom tag library that is used on the page.
- Define Session Management in Java Programming?
A session is defined as the random conversation’s dynamic state between the client and the server.
The virtual communication channel includes a string of responses and requests from both sides.
The easiest and most familiar way of implementing session management is establishing a session ID in the client’s communicative discourse and the server.
- Write a program that detects the duplicate characters in a string
Following is the code in Java that detects duplicate characters in a string
package SoftlogicJava;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
public class FindDuplicate
{
public static void main(String args[])
{
printDuplicateCharacters(“Softlogic”);
}
public static void printDuplicateCharacters(String word)
{
char[] characters = word.toCharArray();
Map < Character, Integer > charMap = new HashMap < Character, Integer > ();
for (Character ch : characters)
{
if charMap.containsKey(ch))
{
charMap.put (ch, charMap.get(ch) + 1);
}
else
{
charMap.put(ch, 1)
}
}
Set < Map.Entry < Character, Integer >> entrySet = charMap.entrySet();
System.out.printf(“The duplicate characters in a String ‘%s’ %n”, word);
for (Map.Entry < Character, Integer > entry : entrySet)
{
if (entry.getValue() > 1)
{
System.out.printf(“%s: %d %n”, entry.getKey(), entry.getValue());
}
}
}
}
Output
The duplicate characters in a String ‘Softlogic’.
o: 2
Conclusion
Gain in-depth knowledge in Java programming in our Softlogic as we provide an experimental learning approach for the students who are fresh graduates and working professionals.
We hope this article helps you get ideas about the interview questions and answers in Java Programming Language.
Enroll today at Softlogic to learn the Best Java Training in Chennai.
