Q12 What Is An Association
Association is a relationship where all object have their own lifecycle and there is no owner. Lets take the example of Teacher and Student. Multiple students can associate with a single teacher and a single student can associate with multiple teachers but there is no ownership between the objects and both have their own lifecycle. These relationships can be one to one, one to many, many to one and many to many.
Java Program To Check If The Given Number Is Prime
We can write a simple program to divide the given number ânâ from 2 to n/2 and check the remainder. If the remainder is 0, then itâs not a prime number.
public class PrimeNumberCheck public static boolean isPrime if for }return true }}
But, this is not very memory and time-efficient. For a given number N, if there is a prime number M between 2 to âN that evenly divides it, then N is not a prime number.
How Null Is Different From Undefined In Javascript
Null: Null means a variable is assigned with a null value. If we use it with typeof operator it gives result as an object. We should never assign a variable to null because the programmer uses it to represent a variable that has no value. Note that JavaScript will never automatically assign the value to null.
Undefined: Undefined means the variable is declared but not assigned any value to it. It may be a variable itself does not exist. If we use it with typeof operator it gives the result undefined. It is not valid in JSON.
Note: Null and undefined both are primitive.
Lets understand it through an example.
When we execute the above code, it generates the following output:
From the above output, we can observe that the value of var1 is undefined also its type is undefined. Because we have not assigned any value to the variable var1. The value null is assigned to the variable var2. It prints its type as abject. Since null is an assignment value and we can assign it to a variable. Therefore, JavaScript treats null and undefined relatively equally because both represent an empty value.
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Q5 Explain The Role Of Dispatcherservlet And Contextloaderlistener
DispatcherServlet is basically the front controller in the Spring MVC application as it loads the spring bean configuration file and initializes all the beans that have been configured. If annotations are enabled, it also scans the packages to configure any bean annotated with @Component, @Controller, @Repository or @Service annotations.
ContextLoaderListener, on the other hand, is the listener to start up and shut down the WebApplicationContext in Spring root. Some of its important functions includes tying up the lifecycle of Application Context to the lifecycle of the ServletContext and automating the creation of ApplicationContext.
Q What Is A Compile Time Constant In Java What Is The Risk Of Using It
If a primitive type or a string is defined as a constant and the value is known at compile time, the compiler replaces the constant name everywhere in the code with its value. This is called a compile-time constant.
Compile time constant must be:
- initialized within declaration
- initialized with constant expression
They are replaced with actual values at compile time because compiler know their value up-front and also knows that it cannot be changed during run-time.
privatefinalintx = 10
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Top Java Interview Questions For Developers With 5 Years Of Experience
We have curated the top Java interview questions for professionals holding 5 yearsâ experience and categorized them according to work experience and important topics such as OOP and thread handling.
Here are some of the most commonly asked Java Interview Questions and Answers for 5 years of Experience.
Q1. Which, according to you, are the most significant features of Java 8?
Answer: Most developers have stuck to the 2014 release, Java 8. It is free for commercial use and has many significant features such as functional interfaces and static methods. It has made programming more simplified and efficient with functional interfaces to object-oriented interfaces.
Q2. What is a Java Class? Can you tell us about some of the common classes of Java?
Answer: A Java Class is a category for Java objects presenting similar properties or methods. It is commonly used as a blueprint for design in object-oriented languages. The most common classes of Java used in app development are static, final, concrete, inner, abstract, and POJO.
Q3. What are the essential concepts to understand in wrapper classes?
Answer: The most significant concepts to understand in wrapper classes are the eight primitive types of wrapper classes and where they are best used. It is important to note that it is final and immutable once a wrapper class is assigned.
Q4. What are the four access modifiers in Java, and where are they used?
Q5. Differentiate between JVM and JDK.
Q6. What is platform independence?
What Is A Static Variable
In Java, we can declare a variable as static, if we declare any variable as static the following can be done, and they are:
- A static variable can be mainly used to refer to all the common properties of objects.
- Memory for the static variable is assigned only once in the class area at the time of class loading
Example for static variable:
//Program of static variable class Mindmajix1 void display public static void main }
Output:
346 Pranaya Appmajix222 Lilly Appmajix
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Common Java Coding Interview Questions About Stacks
Determine whether your candidates knowledge of stacks in Java stacks up to your expectations by asking them some of these 10 interview questions.
Q1 What Is The Difference Between Error And Exception
An error is an irrecoverable condition occurring at runtime. Such as OutOfMemory error. These JVM errors you cannot repair them at runtime. Though error can be caught in the catch block but the execution of application will come to a halt and is not recoverable.
While exceptions are conditions that occur because of bad input or human error etc. e.g. FileNotFoundException will be thrown if the specified file does not exist. Or a NullPointerException will take place if you try using a null reference. In most of the cases it is possible to recover from an exception (probably by giving the user feedback for entering proper values etc.
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Q10 What Is Final Keyword In Java Give An Example
Ans: In java, a constant is declared using the keyword Final. Value can be assigned only once and after assignment, value of a constant cant be changed.
In below example, a constant with the name const_val is declared and assigned avalue:
Private Final int const_val=100
When a method is declared as final, it can NOT be overridden by the subclasses. This method are faster than any other method, because they are resolved at complied time.
When a class is declares as final, it cannot be subclassed. Example String, Integer and other wrapper classes.
What Happens If We Declare A Method As Static
If we declare a method as static, the following operations take place, and they are:
- A static method can be invoked without creating an instance of the class.
- Only a static method can access static data members and can change the value of a particular data member.
- In most of the cases static method belongs to the class rather than the object of the class.
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Find 5 Mistakes In The Following Code Snippet
package com.journaldev.programming-interviews public class String Programs }
Q3 What Is Abstraction In Java
Abstraction refers to the quality of dealing with ideas rather than events. It basically deals with hiding the details and showing the essential things to the user. Thus you can say that abstraction in Java is the process of hiding the implementation details from the user and revealing only the functionality to them. Abstraction can be achieved in two ways:
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Java Coding Interview Questions
Lets go beyond Java basic interview questions and look at some Java programming interview questions used to test the knowledge of candidates. Below are the first 10 of the Top 100 Java Coding Interview Questions.
- How to reverse a String in Java? Can you write a program without using any Java inbuilt methods?
- Write a Java program to check if two Strings are anagram in Java.
- Write a program to check if String has all unique characters in Java.
- How to check if one String is rotation of another String in Java?
- How to find duplicate characters in String in Java?
- Find first non-repeated character in String in Java?
- Find all substrings of String in Java.
- Find length of String without using any inbuilt method in Java.
- Write a program to print all permutations of String in Java.
- Write Java Program to Find Smallest and Largest Element in an Array.
As you can see, these are Java coding interview questions for experienced professionals. They ask the candidate to complete coding tasks and might be used during a whiteboard interview. But without any software engineer behavioral interview questions, these prompts only scratch the surface of a candidates technical skill and ability.
Q42 Can A Class Be A Super Class And A Sub
Ans: If there is a hierarchy of inheritance used, a class can be a super class for another class and a sub-class for another one at the same time.
In the example below, continent class is sub-class of world class and its super class of country class.
public class world public class continenet extends world public class country extends continent
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How To Login To Any Site If It Is Showing An Authentication Pop
To handle authentication pop-ups, verify its appearance and then handle them using an explicit wait command.
Use the explicit wait command
WebDriverWait wait = new WebDriverWait
Alert class is used to verify the alert
Alert alert = wait.until)
Once verified, provide the credentials
alert.authenticateUsing)
Q 60 Explain Failfast Iterator And Failsafe Iterator Along With Examples For Each
FailFast iterators and FailSafe iterators are used in Java Collections.
FailFast iterators do not allow changes or modifications to the Java Collections, which means they fail when the latest element is added to the collection or an existing element gets removed from the collection. The FailFast iterators tend to fail and throw an exception called ConcurrentModificationException.
Ex: ArrayList, HashMap
Whereas, on the other hand, FailSafe iterators allow changes or modifications to be done on the Java Collections. It is possible, as the FailSafe iterators usually operate on the cloned copy of the collection. Hence, they do not throw any specific exception.
Ex: CopyOnWriteArrayList
The string can be reversed by using the following program.
package simplilearnJava
public static void main {
String str = “Simplilearn”
System.out.printf
public static String reverse {
if ) {
1 2 3 4 11 12 13 14 21 22 23 24 31 32
Second Highest is:31
The highest number is: 32
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Java Thread Interview Questions For Developers With 5 Years Experience
When preparing for your Java Advanced interview, you should also practice some Java Thread interview questions and answers for 5 years of experienced professionals. Here are some sample Java Thread interview questions:
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Leave no stone unturned for your Java interview preparation. Study every aspect of a Java interview for developers with 5 years of experience. Be thorough about programming data structures and algorithms, systems design, and specific domain know-how about JavaScript, along with in-depth preparation for behavioral and leadership interview rounds. Experts recommend practicing mock interviews and Java interview questions before you face the actual interview to boost your confidence and prepare you for all kinds of interview situations.
At Interview Kickstart, you can practice mock interviews with experts and hiring managers from FAANG companies. Their valuable feedback has gone a long way in helping Java professionals such as yourself crack tech interviews at the top FAANG companies.
Q What Are The Restrictions That Are Applied To The Java Static Methods
If a method is declared as static, it is a member of a class rather than belonging to the object of the class. It can be called without creating an object of the class. A static method also has the power to access static data members of the class.
- There are a few restrictions imposed on a static method
- The static method cannot use non-static data member or invoke non-static method directly.
- The this and super cannot be used in static context.
- The static method can access only static type data .
- There is no need to create an object of the class to invoke the static method.
- A static method cannot be overridden in a subclass
classParent }publicclassExampleextendsParent publicstaticvoidmain }
This generates a compile time error. The output is as follows
Example.java:10: error: display in Example cannot override display in Parentvoid display // trying to override display ^overridden method is static1 error
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Write A Program In Java To Show Nesting Of Classes
Nesting of classes means writing a class inside another class. The inner classes in Java are usually static. This happens when we dont want to use the variable of the outer class in the inner class. This helps to create an instance/object of the inner class without creating an instance of the Outer class. Following is a program to show the nesting of classes in Java.
Java Code
publicclassMain}classOuter Outer voidshowDataclassInner1 Inner1 voidshowData }staticclassInner2 Inner2 voidshowData }staticclassInner3 Inner3 voidshowData }}
Output
The value of z is: 40100
Can We Overload The Constructors
Yes, the constructors can be overloaded by changing the number of arguments accepted by the constructor or by changing the data type of the parameters. Consider the following example.
In the above program, The constructor Test is overloaded with another constructor. In the first call to the constructor, The constructor with one argument is called, and i will be initialized with the value 10. However, In the second call to the constructor, The constructor with the 2 arguments is called, and i will be initialized with the value 15.
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What Do You Understand By Java Virtual Machine
Java Virtual Machine is a virtual machine that enables the computer to run the Java program. JVM acts like a run-time engine which calls the main method present in the Java code. JVM is the specification which must be implemented in the computer system. The Java code is compiled by JVM to be a Bytecode which is machine independent and close to the native code.
Basic Java Interview Questions
Irrespective of your levels of experience or skills, you may encounter these basic Java interview questions:
-
Which Java project did you enjoy working on the most?
-
Have you ever used Java to manage a team?
-
Which object-orientated programming concepts have you used?
-
Have you used a Request Dispatcher in a project?
-
What do you know about JRE, JVM and JDK in Java?
-
What do you know about wrapper classes in Java?
-
Can you list the differences between the Array list and vector?
-
Can you list the differences between Heap and Stack Memory?
-
Does the garbage collection process clean Heap or Stack Memory?
-
What are the advantages of Java packages?
-
How would you define a Java Class?
-
What are the main OOP concepts in Java?
-
How would you reverse a string in Java?
-
How would you compare two strings in Java?
-
What do you know about API in Java?
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Can This Keyword Be Used To Refer Static Members
Yes, It is possible to use this keyword to refer static members because this is just a reference variable which refers to the current class object. However, as we know that, it is unnecessary to access static variables through objects, therefore, it is not the best practice to use this to refer static members. Consider the following example.
Output
10
Q What Is The Purpose Of The Runtime Class And System Class
Runtime Class: The purpose of the Runtime class is to provide access to the Java runtime system. The runtime information like memory availability, invoking the garbage collector, etc.
System Class: The purpose of the System class is to provide access to system resources. It contains accessibility to standard input, standart output, error output streams, current time in millis, terminating the application, etc.
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Q10 How To Integrate Spring And Hibernate Frameworks
We can use Spring ORM module to integrate Spring and Hibernate frameworks if you are using Hibernate 3+ where SessionFactory provides current session, then you should avoid using HibernateTemplate or HibernateDaoSupport classes and better to use DAO pattern with dependency injection for the integration.
Also, Spring ORM provides support for using Spring declarative transaction management, so you should utilize that rather than going for hibernate boiler-plate code for transaction management.
