100+ Software Engineer Trainee Interview Questions and Answers for Freshers

Program to print the length of number of permutations of a given input

• Use recursion to generate all permutations

• Count the number of permutations and print the length

Java 8 features include lambda expressions, functional interfaces, streams, and default methods.

• Lambda expressions allow you to write code in a more concise and readable way.

• Functional interfaces are interfaces with a single abstract method, used for lambda expressions.

• Streams provide a way to work with sequences of elements and perform operations like filter, map, and reduce.

• Default methods allow interfaces to have method implementations.

• Example: (1) Lambda expression - (a, ...read more

Swap 2 integers without using 3rd integer

• Use XOR operator

• Addition and subtraction can also be used

• Bitwise operations can be used

Given an array of n-1 numbers 1<=a[i]<=n, find the missing number.

• Calculate the sum of all numbers from 1 to n using the formula n*(n+1)/2

• Calculate the sum of all elements in the array

• Subtract the sum of array elements from the sum of all numbers to get the missing number

Private and special IP addresses are reserved ranges of IP addresses used for specific purposes.

• Private IP addresses are used within a private network and are not routable on the internet.

• Special IP addresses include loopback address (127.0.0.1) and broadcast address (255.255.255.255).

• Private IP ranges include 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255, and 192.168.0.0 to 192.168.255.255.

To find leap year using single if condition

• Check if year is divisible by 4 and not divisible by 100

• Or check if year is divisible by 400

• If either of the above conditions is true, then it's a leap year

To reverse a string of a particular order separated by dots, split the string into an array, reverse the array, and join it back into a string.

• Split the string using the dot separator

• Reverse the resulting array

• Join the array back into a string using the dot separator

I would use a combination of HTML, CSS, and JavaScript to create a simple web application that stores and displays data.

• Use HTML to create the structure of the web application

• Use CSS to style the elements on the page

• Use JavaScript to handle user interactions and store/retrieve data

• Consider using a backend server (e.g. Node.js) to handle data storage and retrieval

• Utilize AJAX to fetch data from the server asynchronously

Key OOP concepts in Java include classes, objects, inheritance, polymorphism, encapsulation, and abstraction.

• Classes: Blueprint for creating objects, containing attributes and methods.

• Objects: Instances of classes that encapsulate data and behavior.

• Inheritance: Allows a class to inherit attributes and methods from another class.

• Polymorphism: Ability to present the same interface for different data types.

• Encapsulation: Bundling data and methods that operate on the data into a ...read more

The OSI Reference Model defines 7 layers that represent different functions in networking.

• Physical Layer - deals with physical connections and signals (e.g. cables, hubs)

• Data Link Layer - manages data transfer between devices on the same network (e.g. Ethernet)

• Network Layer - handles routing and forwarding of data packets (e.g. IP)

• Transport Layer - ensures reliable data delivery (e.g. TCP)

• Session Layer - establishes, maintains, and terminates connections (e.g. SSL)

• Presentatio...read more

Use concatenation operator to add two strings.

• Use '+' operator to concatenate two strings.

• Example: str1 + str2 will result in '12348765'.

Method overloading involves multiple methods in the same class with the same name but different parameters. Method overriding involves a subclass providing a specific implementation of a method that is already provided by its superclass.

• Method overloading is achieved within the same class by having multiple methods with the same name but different parameters.

• Method overriding occurs in a subclass that provides a specific implementation of a method that is already provided by ...read more

I used the Dijkstra's algorithm for finding the shortest path in my project.

• Implemented Dijkstra's algorithm to find the shortest path between nodes in a graph

• Used priority queue to optimize the algorithm

• Considered edge weights and node distances while calculating the shortest path

ReactJS life cycle refers to the series of methods that are invoked in the process of creating, updating and destroying a component.

• ReactJS life cycle consists of three phases: Mounting, Updating and Unmounting.

• Mounting phase includes methods like constructor, render, componentDidMount.

• Updating phase includes methods like shouldComponentUpdate, render, componentDidUpdate.

• Unmounting phase includes method componentWillUnmount.

• These methods help in managing the state and props o...read more

Reverse a string using array manipulation

• Create an array of characters from the input string

• Use a loop to iterate through the array in reverse order

• Append each character to a new string to form the reversed string

Dependency injection is a design pattern that allows for better code modularity and testing by injecting dependencies at runtime.

• Promotes loose coupling between classes by injecting dependencies rather than hardcoding them.

• Spring Boot uses annotations like @Autowired, @Component, and @Service to manage dependencies.

• Example: A service class can be injected into a controller using @Autowired, allowing for easier testing and maintenance.

• Supports different types of dependency inj...read more

final, finally, and finalize() serve different purposes in Java: controlling variable scope, exception handling, and garbage collection.

• final: Used to declare constants or prevent method overriding and inheritance. Example: final int x = 10;

• finally: A block that executes after try-catch, regardless of exceptions. Example: try { ... } catch { ... } finally { ... }

• finalize(): A method called by the garbage collector before an object is removed. Example: protected void finalize(...read more

getDerivedStateFromProps() updates state based on props changes. getSnapshotBeforeUpdate() captures current state before update.

• getDerivedStateFromProps() is called before rendering and updates state based on changes in props.

• getSnapshotBeforeUpdate() is called after rendering but before updating the DOM. It captures current state before update.

• getDerivedStateFromProps() is a static method and should return an object to update state or null to indicate no update.

• getSnapshotBe...read more

Code to merge two sorted arrays

• Create a new array to store the merged result

• Use two pointers to iterate through both arrays and compare elements

• Add the smaller element to the new array and move the pointer for that array

Integrity constraints are rules that ensure data integrity and consistency in a database.

• Integrity constraints are used to enforce business rules or data quality rules in a database.

• They can include rules such as unique constraints, foreign key constraints, and check constraints.

• Unique constraints ensure that no two rows have the same value in a specified column.

• Foreign key constraints enforce referential integrity by ensuring that values in one table match values in another ...read more

Exception handling is a mechanism to handle runtime errors in a program to prevent it from crashing.

• Exceptions are unexpected events that occur during the execution of a program.

• Exception handling allows the programmer to gracefully handle these errors and prevent the program from crashing.

• Common exception handling constructs include try, catch, and finally blocks.

• Example: try { // code that may throw an exception } catch(Exception e) { // handle the exception }

• Example: final...read more

Inheritance is a mechanism where a new class is derived from an existing class. Encapsulation is the process of hiding implementation details from the user.

• Inheritance allows the new class to inherit properties and methods of the existing class.

• Encapsulation helps in achieving data abstraction and security.

• Inheritance promotes code reusability while encapsulation promotes data security.

• Example of inheritance: class Car extends Vehicle

• Example of encapsulation: private variable...read more

OOPS Concepts are fundamental principles of Object-Oriented Programming.

• Encapsulation - bundling of data and methods that operate on that data

• Inheritance - ability of a class to inherit properties and methods from its parent class

• Polymorphism - ability of objects to take on multiple forms

• Abstraction - hiding of complex implementation details from the user

• Example code: class Car { private String make; public void setMake(String make) { this.make = make; } }

Local Storage, Session Storage, and Cache are used to store data in the browser for faster access and better user experience.

• Local Storage: stores data with no expiration date and can be accessed across multiple windows and tabs

• Session Storage: stores data for a single session and is cleared when the session ends

• Cache: stores data temporarily to reduce server load and improve performance

• Examples: storing user preferences, caching images and scripts for faster page load

Combine two tables with identical columns in SQL Server without using traditional joins, leveraging UNION or subqueries instead.

• Use UNION to combine results from both tables: SELECT * FROM Table1 UNION SELECT * FROM Table2;

• UNION ALL can be used if you want to include duplicate rows: SELECT * FROM Table1 UNION ALL SELECT * FROM Table2;

• Subqueries can also be utilized: SELECT * FROM (SELECT * FROM Table1) AS T1, (SELECT * FROM Table2) AS T2;

• Ensure both tables have the same numbe...read more

Delete, drop, and truncate are SQL commands for removing data, but they differ in scope and performance.

• DELETE removes specific rows based on a condition. Example: DELETE FROM table WHERE id = 1;

• DROP removes an entire table or database. Example: DROP TABLE table_name;

• TRUNCATE removes all rows from a table but keeps its structure. Example: TRUNCATE TABLE table_name;

• DELETE is slower as it logs each row deletion, while TRUNCATE is faster as it doesn't log individual row deletion...read more

Databases are essential for storing, organizing, and retrieving large amounts of data efficiently.

• Databases provide a structured way to store and manage data.

• They allow for efficient retrieval of data through queries.

• Databases can handle large amounts of data and ensure data integrity.

• They enable multiple users to access and modify data simultaneously.

• Examples include MySQL, Oracle, MongoDB, and SQL Server.