Hooghly Dock & Port Engineers Interview Questions and Answers

Q1. Easy basics questions asked
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Q1. Easy basics questions asked
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Q1. System design was asked
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Q1. Asked core java question
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Q1. Asked dsa questions
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Technical

Q1. Tell me about yourself.
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Q2. What is your current CTC
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Q3. No any other interview
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Q1. Personal qualification
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Q2. Asked to sell a pen
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Q1. What were your reasons for leaving your previous company?
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Q2. What motivates you to seek employment with this company?
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Q1. Tell me about yourself and work experience
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Q2. Past experience of yours
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Q3. Can you adopt to this buisness
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Q1. Explain the difference between ArrayList and LinkedList in Java. When would you choose one over the other?
Ans. 
ArrayList uses dynamic arrays, while LinkedList uses doubly linked nodes for storage, affecting performance and memory usage.
• ArrayList is backed by a dynamic array, allowing fast random access (O(1)). Example: ArrayList<String> list = new ArrayList<>();

• LinkedList is backed by a doubly linked list, allowing efficient insertions and deletions (O(1) at both ends). Example: LinkedList<String> list = new L...read more
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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?
Ans. 
Java's synchronized keyword provides thread safety but has limitations compared to ReentrantLock.
• Advantages of synchronized: Simple to use and understand.

• Disadvantages of synchronized: Can lead to thread contention and performance issues.

• ReentrantLock allows more flexibility, such as tryLock() and timed lock attempts.

• ReentrantLock can be used for fair locking, preventing thread starvation.

• Synchronized blocks are tied t...read more
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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?
Ans. 
In Java, '==' checks reference equality, while '.equals()' checks value equality. Use them appropriately to avoid bugs.
• == compares object references, checking if both refer to the same memory location.

• Example: String a = new String('test'); String b = new String('test'); a == b returns false.

• .equals() compares the actual content of the objects.

• Example: a.equals(b) returns true in the above case.

• Use '==' for primitive t...read more
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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?
Ans. 
Java's garbage collector automatically manages memory by reclaiming unused objects, enhancing performance and preventing memory leaks.
• Java uses automatic garbage collection to manage memory, freeing developers from manual memory management.

• The main garbage collection algorithms in Java include: Serial GC, Parallel GC, Concurrent Mark-Sweep (CMS), and G1 GC.

• Serial GC is a simple, single-threaded collector suitable for s...read more
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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?
Ans. 
Java 8 introduced lambdas, Stream API, and other features that enhance functional programming and simplify code.
• Lambdas: Enable concise representation of functional interfaces. Example: (x, y) -> x + y.

• Stream API: Allows processing sequences of elements (collections) in a functional style. Example: list.stream().filter(x -> x > 10).collect(Collectors.toList()).

• Default Methods: Interfaces can have methods with ...read more
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Q6. Describe the differences between checked and unchecked exceptions in Java. Provide examples and explain how to handle them properly.
Ans. 
Checked exceptions must be declared or handled, while unchecked exceptions do not require explicit handling.
• Checked exceptions are subclasses of Exception (excluding RuntimeException). Example: IOException.

• Unchecked exceptions are subclasses of RuntimeException. Example: NullPointerException.

• Checked exceptions must be caught or declared in the method signature using 'throws'.

• Unchecked exceptions can be caught but are n...read more
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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?
Ans. 
The Java Memory Model defines how threads interact through memory, ensuring visibility and ordering of shared variables.
• The Java Memory Model (JMM) specifies how threads interact with memory, ensuring consistency and visibility of shared variables.

• It defines rules for visibility, atomicity, and ordering of operations, crucial for multithreading.

• Without proper synchronization, threads may see stale data due to caching o...read more
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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.
Ans. 
Method overloading allows multiple methods with the same name but different parameters; overriding redefines a method in a subclass.
• Method Overloading: Same method name, different parameter types or counts.

• Example of Overloading: 'int add(int a, int b)' and 'double add(double a, double b)'.

• Use Overloading for convenience and readability when performing similar operations.

• Method Overriding: Redefining a method in a subc...read more
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Q1. Explain the difference between ArrayList and LinkedList in Java. When would you choose one over the other?
Ans. 
ArrayList is dynamic and index-based, while LinkedList is node-based and allows for efficient insertions and deletions.
• ArrayList uses a dynamic array to store elements, allowing for fast random access. Example: ArrayList<String> arrayList = new ArrayList<>();

• LinkedList uses a doubly linked list structure, making it efficient for insertions and deletions. Example: LinkedList<String> linkedList = new Li...read more
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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?
Ans. 
Java's synchronized keyword offers thread safety but has limitations compared to ReentrantLock.
• Advantages of synchronized: Simple to use, built-in language feature.

• Disadvantages of synchronized: Can lead to thread contention and deadlocks.

• ReentrantLock allows more flexibility, such as tryLock() for non-blocking attempts.

• ReentrantLock supports fairness policies, which can prevent thread starvation.

• Synchronized blocks ar...read more
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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?
Ans. 
== checks reference equality, while .equals() checks value equality in Java objects.
• == compares memory addresses (references) of objects.

• Example: String a = new String("test"); String b = new String("test"); a == b returns false.

• .equals() compares the actual content of objects.

• Example: a.equals(b) returns true for the same content.

• Use == for primitive types (int, char, etc.) and .equals() for object comparisons.

• Imprope...read more
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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?
Ans. 
Java's garbage collector automatically manages memory by reclaiming unused objects, improving performance and preventing memory leaks.
• Java uses automatic memory management to free up memory occupied by objects that are no longer in use.

• The main types of garbage collection algorithms in Java include: Serial, Parallel, Concurrent Mark-Sweep (CMS), and G1 (Garbage-First).

• The Serial Garbage Collector is simple and suitable...read more
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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?
Ans. 
Java 8 introduced lambdas, Stream API, and other features that enhance functional programming and improve code readability.
• Lambda Expressions: Allow for concise representation of functional interfaces. Example: (a, b) -> a + b.

• Stream API: Enables functional-style operations on collections. Example: list.stream().filter(x -> x > 10).collect(Collectors.toList()).

• Default Methods: Interfaces can have methods with ...read more
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Q6. Describe the differences between checked and unchecked exceptions in Java. Provide examples and explain how to handle them properly.
Ans. 
Checked exceptions must be declared or handled, while unchecked exceptions do not require explicit handling.
• Checked exceptions are subclasses of Exception but not of RuntimeException.

• Example of checked exception: IOException, which must be handled or declared.

• Unchecked exceptions are subclasses of RuntimeException.

• Example of unchecked exception: NullPointerException, which does not need to be declared.

• Checked exception...read more
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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?
Ans. 
The Java Memory Model defines how threads interact through memory, ensuring visibility and ordering of shared variables.
• The Java Memory Model (JMM) specifies how threads read and write shared variables.

• It ensures visibility of changes made by one thread to others, preventing stale data.

• Synchronization mechanisms (like synchronized blocks) enforce mutual exclusion and visibility.

• The 'volatile' keyword ensures that a var...read more
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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.
Ans. 
Method overloading allows multiple methods with the same name but different parameters, while overriding replaces a superclass method in a subclass.
• Method Overloading: Same method name, different parameter types or counts.

• Example of Overloading: 'int add(int a, int b)' and 'double add(double a, double b)'.

• Use Overloading for convenience and readability when methods perform similar functions.

• Method Overriding: Same meth...read more
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Q1. Explain the difference between ArrayList and LinkedList in Java. When would you choose one over the other?
Ans. 
ArrayList uses dynamic arrays, while LinkedList uses doubly linked nodes for storage, affecting performance and use cases.
• ArrayList is backed by a dynamic array, allowing fast random access (O(1)). Example: accessing element at index 5 is quick.

• LinkedList consists of nodes that hold data and references to the next and previous nodes, making insertions/removals faster (O(1)).

• ArrayList has a fixed size; resizing involves...read more
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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?
Ans. 
Java's synchronized keyword offers thread safety but has limitations compared to ReentrantLock.
• Advantages of synchronized: Simple to use and understand.

• Disadvantages of synchronized: Can lead to thread contention and deadlocks.

• ReentrantLock allows more flexibility, such as tryLock() and timed lock attempts.

• ReentrantLock can be used for fair locking, preventing thread starvation.

• Synchronized blocks are tied to the objec...read more
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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?
Ans. 
In Java, '==' checks reference equality, while '.equals()' checks value equality. Use them appropriately to avoid bugs.
• == compares object references, checking if both refer to the same memory location.

• Example: String a = new String('test'); String b = new String('test'); a == b returns false.

• .equals() compares the actual content of the objects.

• Example: a.equals(b) returns true since both strings have the same value.

• Use...read more
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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?
Add your answer
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?
Ans. 
Java 8 introduced lambdas, Stream API, and other features that enhance functional programming and simplify code.
• Lambdas: Enable concise representation of functional interfaces. Example: (x, y) -> x + y.

• Stream API: Facilitates functional-style operations on collections. Example: list.stream().filter(x -> x > 10).collect(Collectors.toList()).

• Default Methods: Allow adding new methods to interfaces without breakin...read more
Answered by AI
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Q6. Describe the differences between checked and unchecked exceptions in Java. Provide examples and explain how to handle them properly.
Ans. 
Checked exceptions must be declared or handled, while unchecked exceptions do not require explicit handling in Java.
• Checked exceptions are subclasses of Exception (excluding RuntimeException). Example: IOException.

• Unchecked exceptions are subclasses of RuntimeException. Example: NullPointerException.

• Checked exceptions must be either caught using try-catch or declared in the method signature with 'throws'.

• Unchecked exce...read more
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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?
Ans. 
The Java Memory Model defines how threads interact through memory, ensuring visibility and ordering of shared variables.
• The Java Memory Model (JMM) specifies how threads read and write shared variables.

• It ensures visibility of changes made by one thread to others, preventing stale data.

• Synchronization mechanisms (like synchronized blocks) enforce mutual exclusion and visibility.

• The 'volatile' keyword ensures that a var...read more
Answered by AI
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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.
Ans. 
Method overloading allows multiple methods with the same name but different parameters; overriding replaces a superclass method in a subclass.
• Method Overloading: Same method name, different parameter lists (type, number, or both).

• Example of Overloading: 'int add(int a, int b)' and 'double add(double a, double b)'.

• Method Overriding: Redefining a method in a subclass that already exists in the superclass.

• Example of Overr...read more
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