10405090xyzabc Software Engineer Interview Questions and Answers

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 an 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)) when at known positions.

• ArrayList has a fi...read more

Java's synchronized keyword offers simple thread safety but has limitations compared to ReentrantLock's flexibility and features.

• Advantages of synchronized: Simple to use, built-in language feature.

• Disadvantages of synchronized: Can lead to thread contention, no timeout options.

• ReentrantLock allows for more advanced features like tryLock() and timed lock acquisition.

• Example of synchronized: synchronized void method() {...read more

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 because the content is the same.

• Use '==' f...read more

Java's garbage collector automatically manages memory by reclaiming unused objects, improving 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, Parallel, Concurrent Mark-Sweep (CMS), and G1 (Garbage-First).

• The Serial GC is a simple, single-threaded collector sui...read more

Java 8 introduced lambdas, Stream API, and other features that enhance functional programming and improve code readability.

• Lambda Expressions: Allow concise representation of single-method interfaces (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: Enable...read more

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: IOException, SQLException are checked exceptions.

• Unchecked exceptions are subclasses of RuntimeException.

• Example: NullPointerException, ArrayIndexOutOfBoundsException are unchecked exceptions.

• Checked exceptions must be caught or d...read more

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 through memory and what behaviors are allowed.

• It ensures visibility of shared variables across threads, preventing stale data issues.

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

• The 'volatile' k...read more

ArrayList uses dynamic arrays, while LinkedList uses linked nodes. Choose based on performance needs for insertion and access.

• ArrayList is backed by a dynamic array, allowing fast random access (O(1)). Example: accessing elements by index.

• LinkedList is backed by a doubly linked list, allowing fast insertions and deletions (O(1)) at both ends. Example: adding/removing elements from the front.

• ArrayList has a fixed size, ...read more

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 deadlocks, less flexible than ReentrantLock.

• ReentrantLock allows for tryLock() method, enabling non-blocking attempts to acquire a lock.

• ReentrantLock supports fairness policies, allowing threads to acquire locks in ...read more

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 because the content is the same.

• Use '==' f...read more

Java's garbage collector automatically manages memory by reclaiming unused objects, improving performance and preventing memory leaks.

• Java uses automatic garbage collection to manage memory, freeing developers from manual memory management.

• 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 suit...read more

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

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

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.

• It defines rules for visibility, atomicity, and ordering of operations in a multithreaded environment.

• Without proper synchronization, threads may see stale or inconsistent data due to caching an...read more

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 types or counts.

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

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

• Method Overriding: Redefining a met...read more