10405090xyzabc Software Engineer Interview Questions and Answers

Q1. Explain the difference between ArrayList and LinkedList in Java. When would you choose one over the other?
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Q2. What are the advantages and disadvantages of using Java’s synchronized keyword for thread synchronization? Can you explain how the ReentrantLock compares to synchronized?
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Q3. What is the difference between == and .equals() in Java? When should each be used, and what issues can arise from improper usage?
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Q4. How does the Java garbage collector work? Can you describe the different types of garbage collection algorithms available in Java?
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Q5. What are the main features of Java 8? Can you explain how lambdas and the Stream API have changed the way Java applications are written?
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Q6. Describe the differences between checked and unchecked exceptions in Java. Provide examples and explain how to handle them properly.
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Q7. What is the Java Memory Model, and how does it affect multithreading and synchronization? How does volatile help ensure memory visibility?
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Q8. Can you explain the difference between method overloading and method overriding in Java? Provide examples where each should be used.
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Q9. What are functional interfaces in Java? How do they work with lambda expressions? Provide an example of a custom functional interface.
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Q10. What is a Java Stream, and how does it differ from an Iterator? Explain how Streams can be used to process collections efficiently.
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Q11. Explain the concept of immutability in Java. How does the String class achieve immutability, and what are the advantages of immutable objects?
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Q12. What is the difference between final, finally, and finalize in Java? Provide examples to illustrate their usage.
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Q13. Explain the Singleton design pattern in Java. How can you implement it safely to ensure thread safety?
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Q14. What are Java annotations, and how are they used in frameworks like Spring? Explain the difference between built-in and custom annotations.
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Q15. How do Java Streams handle parallel processing? What are the potential pitfalls of using parallel streams, and how can they be mitigated?
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Q16. Explain the difference between ArrayList and LinkedList in Java. ArrayList is implemented as a dynamic array, while LinkedList is a doubly linked list. ArrayList provides fast random access (O(1) complexi...read more
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Q17. What are the advantages and disadvantages of using Java’s synchronized keyword for thread synchronization? The synchronized keyword ensures that only one thread can access a block of code at a time. It pr...read more
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Q18. What is the difference between == and .equals() in Java? == checks for reference equality, meaning it compares memory addresses. equals() checks for value equality, which can be overridden in user-defined...read more
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Q19. How does the Java garbage collector work? Garbage collection in Java automatically reclaims memory occupied by unused objects. The JVM has different types of GC algorithms, including Serial, Parallel, CMS...read more
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Q20. What are the main features of Java 8? Java 8 introduced lambda expressions, enabling functional-style programming. The Stream API allows efficient data processing with map, filter, and reduce operations. ...read more
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Q1. What is a transaction in DBMS, what are ACID properties? Explain the difference between SQL and NoSQL databases. How would you optimize a slow running query?
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A transaction in DBMS is a unit of work that must be executed as a whole. ACID properties ensure data integrity. SQL is relational, NoSQL is non-relational.
• A transaction in DBMS is a set of operations that must be executed as a single unit.

• ACID properties (Atomicity, Consistency, Isolation, Durability) ensure data integrity in transactions.

• SQL databases are relational and use structured query language, while NoSQL data...read more
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Q2. Define encapsulation and provide an example. Discuss the principles of inheritance and polymorphism.
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Encapsulation is the concept of bundling data and methods that operate on the data into a single unit. Inheritance allows a class to inherit attributes and methods from another class. Polymorphism allows objects of different classes to be treated as objects of a common superclass.
• Encapsulation helps in data hiding and abstraction

• Example: A class 'Car' encapsulates data like make, model, and methods like start(), stop()

• ...read more
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Q3. Explain how to detect a cycle in a linked list.
Ans. 
Use Floyd's Tortoise and Hare algorithm to detect a cycle in a linked list.
• Start with two pointers, slow and fast, moving at different speeds.

• If there is a cycle, the two pointers will eventually meet at some point.

• If there is no cycle, the fast pointer will reach the end of the list.

• Example: 1->2->3->4->5->2 (cycle at node 2), slow and fast pointers will meet at node 2.
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First round was based on logical questions and was taken on hacker earth

Q1. First question was based on rotating a matrix by 90 degrees
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