QBurst Technologies Interview Questions and Answers

Q1. Explain singleton design pattern.
Ans. 
The singleton design pattern ensures a class has only one instance and provides a global point of access to it.
• Restricts instantiation of a class to a single object.

• Provides a global access point to that instance.

• Commonly used for configuration settings, logging, and thread pools.

• Example in Java: Use a private constructor and a static method to get the instance.

• Thread-safe implementations can be achieved using synchron...read more
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Q2. Streaming query to get frequently occurring character.
Ans. 
Use Java Streams to count character occurrences in a string and find the most frequent one efficiently.
• Utilize Java Streams to process the string: `string.chars()` converts to an IntStream.

• Group characters using `Collectors.groupingBy()` to count occurrences.

• Sort the map by values to find the maximum occurrence: `map.entrySet().stream().max(Map.Entry.comparingByValue())`.

• Example: For input 'hello', the output should be...read more
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Q3. SQL query for outer join scenario
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An outer join retrieves records from both tables, including unmatched rows from one or both sides.
• Outer joins can be LEFT, RIGHT, or FULL, depending on which table's unmatched rows you want to include.

• Example of LEFT JOIN: SELECT * FROM A LEFT JOIN B ON A.id = B.a_id; // Includes all from A and matched from B.

• Example of RIGHT JOIN: SELECT * FROM A RIGHT JOIN B ON A.id = B.a_id; // Includes all from B and matched from A...read more
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Q1. Questions related to Jwt token
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Q2. Questions related to current project architecture
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3 questions
1. Check the given string is reversed?
input: "worldhello" output: "true"
2. Check the given string is permutation of palindrome?
3. Sort a stack using an empty stack

Q1. Javascript basics
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Q2. Nodejs basics questions
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Q1. How do GO handle concurrency?
Ans. 
GO uses goroutines and channels to handle concurrency efficiently.
• GO uses goroutines to achieve concurrency. Goroutines are lightweight threads managed by the Go runtime.

• Channels are used to communicate between goroutines. They provide a safe way to pass data between concurrent processes.

• GO also has a built-in 'sync' package for synchronization primitives like mutexes and wait groups.

• GO's 'select' statement allows for ...read more
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Q2. What is defer in GO ? If there are multiple defers in a function, what will be order of execution of these?
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defer in Go is used to delay the execution of a function until the surrounding function returns.
• Defer is used to ensure that a function call is performed at the end of the surrounding function, regardless of where the defer statement is located.

• If there are multiple defers in a function, they will be executed in Last In, First Out (LIFO) order.

• Example: func exampleFunc() { defer fmt.Println('First defer'); defer fmt.Pr...read more
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Q1. Memory leak in Android?
Ans. 
Memory leak in Android refers to a situation where an application uses memory inefficiently, causing unused memory to accumulate and not be released.
• Memory leaks can occur when objects are not properly released after use, leading to a buildup of unused memory.

• Common causes of memory leaks in Android include holding onto references to objects that are no longer needed, using static variables in a way that prevents them ...read more
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Q2. Garbage collection basics.
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Q3. Pass data between fragments in Android
Ans. 
Use ViewModel to share data between fragments in Android
• Create a ViewModel class to hold the data to be shared

• Observe the ViewModel in each fragment to receive updates

• Use LiveData to ensure data is updated in real-time
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Q1. Implement a Hash Map
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A Hash Map is a data structure that stores key-value pairs and allows for fast retrieval of values based on keys.
• Use an array to store the key-value pairs

• Implement a hash function to map keys to indices in the array

• Handle collisions by using techniques like chaining or open addressing
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Q2. Activity lifecycle in Android
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Activity lifecycle in Android refers to the different states an activity goes through during its lifetime.
• There are several states in the activity lifecycle, including onCreate, onStart, onResume, onPause, onStop, and onDestroy.

• Activities can transition between these states based on user interactions or system events.

• Understanding the activity lifecycle is crucial for managing resources and maintaining a smooth user ex...read more
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