Prolifics Corporation Fullstack Java Developer Interview Questions and Answers

Q1. Internal working of hashmap
Ans. 
HashMap is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values.
• HashMap internally uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to find the index in the array where it will be stored.

• If multiple keys hash to the same index, a linked list is used to handle collisions.

• HashMap allows one null key and multiple null values.

• Th...read more
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Q2. What is singleton class and its implementation
Ans. 
Singleton class is a class that can only have one instance and provides a global point of access to it.
• Singleton class restricts the instantiation of a class to one object.

• It provides a way to access its unique instance globally.

• Commonly used in scenarios where only one instance of a class is needed, such as database connections or thread pools.
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Q3. Find all the pairs with given sum coding
Ans. 
The task is to find all pairs in an array that add up to a given sum.
• Iterate through the array and store each element in a hash set.

• For each element, check if the difference between the sum and the element exists in the hash set.

• If it does, add the pair to the result list.
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One question on Java on reversing only the numbers in an array
One question on React to build search component

Q1. Fundamentals in java, react and spring
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Q1. Differences between promises and observables
Ans. 
Promises are used for a single async operation while observables handle multiple async operations and can be cancelled.
• Promises are eager, meaning they start immediately upon creation.

• Observables are lazy, meaning they only start when subscribed to.

• Promises can only handle a single value or error, while observables can handle multiple values over time.

• Observables can be cancelled, while promises cannot be cancelled.

• Pro...read more
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Q2. Angular vs react differences
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Angular and React are both popular front-end frameworks, but they have some key differences in terms of architecture, syntax, and ecosystem.
• Angular is a full-fledged framework with a steep learning curve, while React is a library that is more flexible and easier to learn.

• Angular uses two-way data binding, while React uses one-way data flow.

• Angular has a more opinionated architecture and provides more out-of-the-box fea...read more
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