15 Java Interview Questions You Need to Learn Now!
15 Java Interview Questions You Need to Learn Now!
Foreword:
Java is surely the most versatile programming language and is ruling the tech industry with its easily compilable feature. It is simple to use, object-oriented, as well as extremely time-saving. You don’t even need to worry about its flexibility and stability.
As a Java developer, you get a wide variety of options to work with it.
Hence, if you’re planning to grow your career as a Java programmer, you need to learn these interview questions that can help you get your dream job, or to say the least, improve your knowledge for a better opportunity.
Java Interview Questions that are asked when you’re a Fresher
The composition of Java is made in such a way, that it doesn’t require any hardware or software to make it run. The fact that compilers can compile it into a platform-independent byte code, it becomes easier to make it work on multiple systems.
2. What is Core Java?
Core Java is the basic form of Java that helps understand the primary functionality of Java Programming. There are a group of technologies related to Java, such as Java Virtual Machine, CORBA, so on and so forth.
3. Explain what is an array.
An array, as we know is a container object that helps in storing a fixed number of values of a single type. We can determine its length by knowing the time of its creation.
Java Interview Questions if you’re an Experienced Professional
JCA or Java Cryptography Architecture is the framework that is used for working with cryptography with Java Programming language.
2. Explain Dynamic Method Dispatch in Java
Dynamic method Dispatch, also known as runtime polymorphism, is a method that is utilized for resolving the overridden method during runtime and not during the compilation of the program. This particular method can be called through a reference variable of a superclass.
3. Give the differences between JAR and WAR files in Java.
The following are the distinctions between a JAR and a WAR file:
The JAR file stands for Java Archive File, which allows us to aggregate multiple files into one. WAR files, on the other hand, are Web Application Archive files that hold XML, Java classes, JavaServer Pages, and other data for Web applications.
A library's Java classes are stored as JAR files. WAR files, on the other hand, save the files in the web application's 'lib' directory.
The EJB module's enterprise Java Bean classes and EJB deployment descriptors are packed and saved in a JAR file with the.jar extension. The WAR file, on the other hand, contains web modules with the “. war” extension, such as Servlet classes, GIFs, HTML files, JSP files, and so on.
Java Interview Questions for Coding
1. How can you Construct a Java program that can tell whether a number is prime or not?
A boolean variable, "isPrime" is set as true. Hence, it is required to use the loop starting from 2. hence, less than half of the number can be entered as well as incremented by 1 for each iteration that's done. The temp will have the remainder for every iteration. If the remainder comes as 0, then "isPrime" will be set to False.
import java.util.Scanner;
public class Prime {
public static void main(String[] args) {
// TODO Auto-generated method stub
int temp, num;
boolean isPrime = true;
Scanner in = new Scanner(System.in);
num = in.nextInt();
in.close();
for (int i = 2; i<= num/2; i++) {
temp = num%i;
if (temp == 0) {
isPrime = false;
break;
}
}
if(isPrime)
System.out.println(num + "number is prime");
else
System.out.println(num + "number is not a prime");
}
}
2. Write a Java program to see if a string or number is palindrome or not.
You can do it by using the if-else statement. If the original string is equal to the reversed string then we can understand the number is a palindrome, otherwise, it is not.
import java.util.Scanner;
public class Palindrome {
public static void main (String[] args) {
String original, reverse = "";
Scanner in = new Scanner(System.in);
int length;
System.out.println("Enter the number or String");
original = in.nextLine();
length = original.length();
for (int i =length -1; i>;=0; i--) {
reverse = reverse + original.charAt(i);
}
System.out.println("reverse is:" +reverse);
if(original.equals(reverse))
System.out.println("The number is palindrome");
else
System.out.println("The number is not a palindrome");
}
}
3. Find the second largest number in an array
int[] arr1={7,5,6,1,4,2};
Second largest element in the array : 6
Here’s how it’s done:
package org.arpit.java2blog;
public class FindSecondLargestMain {
public static void main(String args[])
{
int[] arr1={7,5,6,1,4,2};
int secondHighest=findSecondLargestNumberInTheArray(arr1);
System.out.println("Second largest element in the array : "+ secondHighest);
}
public static int findSecondLargestNumberInTheArray(int array[])
{
// Initialize these to the smallest value possible
int highest = Integer.MIN_VALUE;
int secondHighest = Integer.MIN_VALUE;
// Loop over the array
for (int i = 0; i < array.length; i++) {
// If current element is greater than highest
if (array[i] > highest) {
// assign second highest element to highest element
secondHighest = highest;
// highest element to current element
highest = array[i];
} else if (array[i] > secondHighest && array[i]!=highest)
// Just replace the second highest
secondHighest = array[i];
}
// After exiting the loop, secondHighest now represents the second
// largest value in the array
return secondHighest;
}
}
Java Interview Questions for Multithreading
A Process is an active program that’s yet to be executed. Being more than just a program code, this includes factors like the program counter, process stack, registers, program code, etc.
In comparison to this, the program code remains as the text section.
The Thread is a lightweight process that is easily managed by a scheduler in an independent manner. Using the method of parallelism helps in improving the performance of an application.
2. Tell the differences between User Thread and Daemon Thread.
Daemon threads are known as the low priority threads which run in the background all the time. User threads, on the other hand, are high-priority threads that run in the foreground all the time.
User Threads or Non-Daemon are created to do specific or complex tasks whereas daemon threads are used to execute the supporting tasks.
3. Give the difference between notify() and notify All().
Object class is Java's top-level class, which defines the notify() method. It is mainly used to wake up only one thread that's been waiting for an object. Only then does that particular thread starts running. To wake up a single thread, utilize the thread class notify() method.
The notifyAll() method helps in waking up all the threads that are waiting on the monitor of this object. By using one of the wait methods, a thread can wait on an object's monitor. If the current thread renounces the lock on this object, the awakened threads will be unable to move any further.
Java OOPS
What do you mean by the term OOPS?
The term OOPs stands for Object-Oriented Programming. It is the programming pattern that defines by using objects.
List down the main features of OOPS.
Inheritance
Encapsulation
Polymorphism
Data Abstraction
What are subclass and superclass?
Subclass and superclass are both parts of inheritance. A subclass is inherited from another class and is also named the child class.
A superclass helps the subclass or child class to inherit itself.
Conclusion:
Java is surely bringing innovation to our world with its well-architectured framework.
If you are applying for jobs or even preparing for an interview, ClassFly is your perfect guide to help you prepare with our pre-interview programs. Leading a successful life is absolutely possible if you know your next step.
Join our pre-interview program today and see the difference yourself.
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