HCLTech Java Developer Interview Questions, Process, and Tips

String is immutable in Java to ensure security, thread safety, and optimization.

• Immutable strings prevent modification, ensuring data integrity and security.

• Immutable strings can be safely shared across multiple threads without synchronization issues.

• Immutable strings allow for efficient memory allocation and string pooling.

• Example: String s = "Hello"; s.concat(" World"); // returns a new string without modifying the o

Cloning is creating an exact copy of an object.

• Cloning is done using the clone() method.

• The cloned object is a separate instance with the same state as the original.

• Changes made to the cloned object do not affect the original object.

• Cloning can be shallow or deep depending on the implementation.

• Example: cloning an ArrayList to create a backup copy.

Preventing hash collisions in Java

• Use a good hash function that distributes keys evenly

• Implement a resizing strategy for hash tables

• Use open addressing or separate chaining to handle collisions

• Consider using a hash table library like Guava or Apache Commons

• Avoid using mutable objects as keys in hash tables

Questions on Java collections, exception handling, multithreading, Spring AOP, MVC, Hibernate session, and programming with maps and strings.

• Explain the differences between HashMap and HashTable and their internal workings.

• Discuss the importance of exception handling and provide examples of how to handle exceptions in Java.

• Explain multithreading and how it can be implemented in Java.

• Discuss the String class and its met...read more

System.out.println is a Java statement used to print output to the console.

• System is a class in Java's core library.

• out is a static member of the System class.

• println is a method of the PrintStream class.

• It is used to print output to the console.

• It adds a newline character at the end of the output.

Static or final method is a method that belongs to a class rather than an instance of the class.

• Static method can be called without creating an instance of the class.

• Final method cannot be overridden by a subclass.

• Static and final methods can be accessed using the class name.

• Example: Math.max() is a static method in the Math class.

• Example: String.toUpperCase() is a final method in the String class.

A collection is a group of objects that can be stored, manipulated, and retrieved as a single unit.

• Collections are used to store and manage groups of related objects.

• Java provides several built-in collection classes such as ArrayList, LinkedList, HashSet, etc.

• Collections can be used to perform operations like sorting, searching, filtering, and more.

• Collections can be generic or non-generic, depending on the type of obj

Yes, we can add string or integer value using map in Java.

• We can use put() method to add values to a map.

• For string values, we can use String as the value type.

• For integer values, we can use Integer as the value type.

• Example: Map map = new HashMap<>(); map.put("key", "value");

• Example: Map map = new HashMap<>(); map.put("key", 123);

Sleep method pauses the thread for a specified time, while wait method pauses the thread until notified.

• Sleep method is a static method of Thread class, while wait method is an instance method of Object class.

• Sleep method does not release the lock on the object, while wait method releases the lock and waits for notification.

• Sleep method can be interrupted by another thread, while wait method can only be interrupted by ...read more

Join in SQL is used to combine rows from two or more tables based on a related column between them.

• Join is used to retrieve data from multiple tables in a single query

• Types of join include inner join, left join, right join, and full outer join

• Join condition is specified using ON keyword

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column

• Join can also be used with subqueries

SQL queries are used to retrieve, manipulate and manage data stored in relational databases.

• SQL stands for Structured Query Language

• Queries can be used to retrieve specific data from tables

• Queries can also be used to update, insert or delete data

• Examples of SQL queries include SELECT, INSERT, UPDATE and DELETE

• Understanding SQL is important for working with databases in Java

Abstraction is a concept of hiding implementation details while interface is a contract that defines the behavior of a class.

• Abstraction is achieved through abstract classes and methods

• Interface is a collection of abstract methods and constants

• Abstraction allows for flexibility in implementation

• Interface allows for multiple inheritance

• Abstraction is used for code reusability

• Interface is used for achieving polymorphism

Overloading is when multiple methods have the same name but different parameters. Overriding is when a subclass provides a different implementation of a method inherited from its superclass.

• Overloading is resolved at compile-time based on the method signature.

• Overriding is resolved at runtime based on the actual object type.

• Overloading is used to provide different ways to call a method with different parameters.

• Overrid...read more

A program to calculate the sum of numbers.

• Create a variable to store the sum.

• Iterate through the numbers and add each number to the sum.

• Return the sum.