Simple Java Coding Interview Questions

Q6 How Does An Exception Propagate In The Code

If an exception is not caught, it is thrown from the top of the stack and falls down the call stack to the previous procedure. If the exception isnt caught there, it falls back to the previous function, and so on, until its caught or the call stack reaches the bottom. The term for this is Exception propagation.

Q The Difference Between Serial And Parallel Garbage Collector

Serial Garbage Collector

Serial garbage collector works by holding all the application threads. It is designed for the single-threaded environments. It uses just a single thread for garbage collection. The way it works by freezing all the application threads while doing garbage collection may not be suitable for a server environment. It is best suited for simple command-line programs.

Turn on the -XX:+UseSerialGC JVM argument to use the serial garbage collector.

Parallel Garbage Collector

Parallel garbage collector is also called as throughput collector. It is the default garbage collector of the JVM. Unlike serial garbage collector, this uses multiple threads for garbage collection. Similar to serial garbage collector this also freezes all the application threads while performing garbage collection.

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Sample Technical Interview Questions: Java

If youre looking for a job in software development or any other role that is highly technical, chances are you will be asked to participate in a technical interview. In this interview youll be given questions that test your technical subject-matter knowledge and ability to apply your skills. You can learn all about technical interviews and how to prepare for them from our Guide to Acing the Technical Interview.

Some technical interviews are generic and ask a wide range of programming questions, but interviews for more specific roles may focus on a single language, like Java. Here weve compiled a list of technical interview questions you may be asked in a Java interview. To learn more about Java and its applications, check out our ultimate guide to Java.

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Q1: What Is The Method To Serialize An Object In Java

Ans: To convert an object into a byte stream by serialization in Java, the class executes an interface with the name Serializable. All the class objects executing serializable interface are serialized, and their state is retained in the byte stream.

If you are going for the interview, it is one of the essential Java technical interview questions that you should know.

How Is Jsp Better Than Servlet Technology

JSP is a technology on the servers side to make content generation simple. They are document-centric, whereas servlets are programs. A Java server page can contain fragments of Java program, which execute and instantiate Java classes. However, they occur inside an HTML template file. It provides the framework for the development of a Web Application.

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What Are The Different Types Of Control Statements In Java

Java has 3 different types of control statements:

• Selection statements: These statements give the option of choosing a different path of execution of a program depending on the result of a test condition. The expressions in this group are if, if-else and switch statement.

• Iteration statements: These statements allow repeated evaluation of a statement or a block of statements if the test condition is satisfied. This group contains a statement such as a while, do-while, for and for-each.

• Jump statements: These statements make the program control jump to another part of the program forward or backward directions with or without a test condition. The statements in this group are break, break label, continue.

Common Java Code Interview Questions

Interviewers usually ask basic Java code questions in interviews along with some theoretical aspects. You might be asked questions or tasks like these:

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Q1: Can A Class Have More Than One Constructor

Ans: Yes. A class can have more than one constructor with various parameters. The usage of the constructor for the object depends on the arguments passed wh8ile establishing the objects.

When you go for the interview, remember it is one of the essential Java interview questions interviewers can ask.

Q What Is Difference Between String Stringbuffer And Stringbuilder

Mutability Difference:String is immutable, if you try to alter their values, another object gets created, whereas StringBuffer and StringBuilder are mutable so they can change their values.

Thread-Safety Difference: The difference between StringBuffer and StringBuilder is that StringBuffer is thread-safe. So when the application needs to be run only in a single thread then it is better to use StringBuilder. StringBuilder is more efficient than StringBuffer.

Example: StringBuffer

publicclassBufferTest  }  

Example: StringBuilder

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Q9 What Are The Differences Between Throw And Throws

In case you are facing any challenges with these java interview questions, please comment on your problems in the section below.

What Are The Differences Between Static And Non

This question is to test your understanding of using static and non-static methods. Your answer can include the use of keywords, compile-time and runtime.

Example answer:”For creating the static method in Java, you must use the static keyword before the method name. With the non-static method, using the static keyword before the name of the method is not necessary. In Java, a static method is part of the class, and a non-static method is part of the object of a class. You do not need to create an instance of the class to access the static method, but creating an instance of the class is essential for accessing the non-static method.

A static method can call only other static methods, not a non-static method, and it can access only static variables, not a non-static variable. A non-static method, on the other hand, can call a static method and access a static variable. The syntax to call a static method using the class is className.methodName. You can call it a non-static method like any method.”

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Java Basic Interview Questions With Answers

If you are discussing Java basics in your interview, you can expect to face questions that give you the opportunity to show off your knowledge. Below are 10 Java interview questions with answers to serve as examples for possible interview situations:

What Are Various Access Specifiers Present In Java

There are four access specifiers present in Java, and they are:

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Q How Garbage Collector Algorithm Works

Garbage collection works on and Sweep algorithm. In Mark phase it detects all the unreachable objects and Sweep phase it reclaim the heap space used by the garbage objects and make the space available again to the program.

There are methods like System.gc and Runtime.gc which is used to send request of Garbage collection to JVM but its not guaranteed that garbage collection will happen. If there is no memory space for creating a new object in Heap Java Virtual Machine throws OutOfMemoryError or java.lang.OutOfMemoryError heap space

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Define For Each Loop In Java

For-each is another kind of array traversing technique in Java which is the same as that of for loop, while loop. It is most commonly used to iterate over a collection or an array such as ArrayList. An example for for-each loop is as follows:

class ForEachPro      //traversing the array with for-each loop   for   }   } 

Output:

12121444

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Why The Main Method Is Static In Java

Java main method is always static, so the compiler can call it without the creation of an object or before the creation of an object of the class. In any Java program, the main method is the starting point from where the compiler starts program execution. So, the compiler needs to call the main method.

Q Java Program To Implement Singly Linked List

The singly linked list is a linear data structure in which each element of the list contains a pointer which points to the next element in the list. Each element in the singly linked list is called a node. Each node has two components: data and a pointer next which points to the next node in the list.

Example:

publicclassSinglyLinkedList         }    // Represent the head and tail of the singly linked list    publicNodehead = null     publicNodetail = null     // addNode will add a new node to the list    publicvoidaddNode     else         }    // display will display all the nodes present in the list    publicvoiddisplay     System.out.println     while     System.out.println         }    publicstaticvoidmain     }  

Output:

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Get Ready For Your Upcoming Technical Interview

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Tricky Java Interview Questions

Here are some tricky interview questions on Java to boost the inner coding interview ninja are listed below.

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Q Do You Know Generics How Did You Used In Your Coding

Generics allows type to be a parameter to methods, classes and interfaces. For example, classes like HashSet, ArrayList, HashMap, etc use generics very well.

Advantages

• Type-safety: We can hold only a single type of objects in generics. It doesn’t allow to store other objects.
• Type Casting: There is no need to typecast the object.
• Compile-Time Checking: It is checked at compile time so problem will not occur at runtime.

Example:

/** * A Simple Java program to show multiple * type parameters in Java Generics ** We use < >  to specify Parameter type***/classGenericClass< T, U>   // To print objects of T and U publicvoidprint  } // Driver class to test above classMainClass  }

Output:

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Array Of Products Of All Elements Except Itself

Problem Statement:

Implement the int findProduct method which will modify arr in such a way that in the output, each index i will contain the product of all elements present in arr except the element stored on that index i.

Solution and Explanation:

class ProductArray       // Initializing temp to 1 for product on right side    temp = 1      // Product of elements on right side excluding arr     for           return result    }   public static String arrayToString      return result     }    else   }  public static void main      System.out.println)     int prodArray = findProduct     System.out.println)   }}

The algorithm for this solution is to first create a new array with products of all elements to the left of each element, as done on lines 17-20.

Then on lines 27-30, multiply each element in that array to the product of all the elements to the right of the array by traversing it in reverse.

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What Is Synchronization In Java

Synchronization is a process of handling resource accessibility by multiple thread requests. The main purpose of synchronization is to avoid thread interference. At times when more than one thread tries to access a shared resource, we need to ensure that the resource will be used by only one thread at a time. The process by which this is achieved is called synchronization. The synchronization keyword in java creates a block of code referred to as a critical section.

Q4 Explain Bean In Spring And List The Different Scopes Of Spring Bean

Beans are objects that form the backbone of a Spring application. They are managed by the Spring IoC container. In other words, a bean is an object that is instantiated, assembled, and managed by a Spring IoC container.

There are five Scopes defined in Spring beans.

• Singleton: Only one instance of the bean will be created for each container. This is the default scope for the spring beans. While using this scope, make sure spring bean doesnt have shared instance variables otherwise it might lead to data inconsistency issues because its not thread-safe.
• Prototype: A new instance will be created every time the bean is requested.
• Request: This is same as prototype scope, however its meant to be used for web applications. A new instance of the bean will be created for each HTTP request.
• Session: A new bean will be created for each HTTP session by the container.
• Global-session: This is used to create global session beans for Portlet applications.

In case you are facing any challenges with these java interview questions, please comment on your problems in the section below.

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General Java Interview Questions For Freshers

Your interviewer might ask you general questions about Java and its use during your interview for a fresher role. Here are some general Java interview questions they might ask:

• Explain wrapper classes in Java.

• What is autoboxing?

• Explain the advantages of object cloning.

• Describe the disadvantages of object cloning.

• What is the strictfp keyword and why is it important?

• Explain the importance of the System class.

• Describe the singleton class.

• Describe the static method and its restrictions.

• Explain the difference between the static method and the instance method.

• How do you use the “this” keyword in Java?

• Describe constructor chaining using the “this” keyword in Java.

• Explain the Inheritance and its use in Java.

• What is a superclass, and what is the Java superclass?

• Define aggregation and its importance in Java.

• Explain the difference between composition and aggregation in Java.

• What is the “super” keyword and how is it used in Java?

• Explain method overloading in Java.

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What Is A Comparator In Java

Consider the example where we have an ArrayList of employees like, etc. Now if we want to sort this list of employees based on the names of employees. Then that is not possible to sort using the Collections.sort method. We need to provide something to the sort function depending on what values we have to perform sorting. Then in that case a comparator is used.

Comparator is the interface in java that contains the compare method. And by overloading the compare method, we can define that on what basis we need to compare the values.

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What Is Object In Java

An object is a software bundle of variables and related methods. You can represent real-world objects using software objects. You might want to represent real-world dogs as software objects in an animation program or a real-world bicycle as a software object within an electronic exercise bike. However, you can also use software objects to model abstract concepts. For example, an event is a common object used in GUI window systems to represent the action of a user pressing a mouse button or a key on the keyboard.

Question : Edit Distance Problem In Java

Given two strings string1 and string2, String1 is to be converted into String2 with the given operations available in the minimum number of steps. Using any one of the given operations contributes to the increment of steps by one.

Allowed Operations are : Remove : This operation allows the Removal any one character from String. Insert : This operation allows the Insertion of one character at any spot in the String. Replace : This operation allows the replacement of any one character in the string withany other character.

Solution: Edit distance problem in java.

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