10405090xyzabc Software Engineer Interview Questions, Process, and Tips

ArrayList is a resizable array, while LinkedList is a doubly linked list. Choose based on performance needs.

• ArrayList: Faster for random access (O(1)). Example: list.get(5);

• LinkedList: Faster for insertions/deletions (O(1)) at both ends. Example: list.addFirst('A');

• ArrayList: Uses less memory overhead compared to LinkedList.

• LinkedList: Better for frequent insertions/deletions in the middle of the list.

• ArrayList: Requir...read more

Java's synchronized keyword provides 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, no timeout options.

• ReentrantLock allows more flexibility: supports tryLock(), lockInterruptibly().

• ReentrantLock can be more efficient in high contention scenarios.

• Example of synchronized: synchr...read more

== checks reference equality, while .equals() checks value equality in Java. Use .equals() for content comparison.

• == compares object references (memory addresses). Example: String a = new String('test'); String b = new String('test'); a == b returns false.

• .equals() compares actual content of objects. Example: a.equals(b) returns true.

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

• Improper use of...read more

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

• Garbage Collection (GC) is the process of automatically identifying and disposing of objects that are no longer needed.

• Java uses several GC algorithms, including Serial, Parallel, CMS (Concurrent Mark-Sweep), 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.

• 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 me...read more

Checked exceptions must be declared or handled; 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 caught or declared.

• Unchecked exceptions are subclasses of RuntimeException.

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

• Checked exceptions are t...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 of shared variables.

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

• Without proper synchronization, threads may see stale or inconsistent da...read more

Method overloading allows multiple methods with the same name but different parameters; overriding allows subclass methods to replace superclass methods.

• 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: Same met...read more

Functional interfaces in Java are interfaces with a single abstract method, enabling lambda expressions for concise code.

• A functional interface has exactly one abstract method.

• They can have multiple default or static methods.

• Common examples include Runnable, Callable, and Comparator.

• Lambda expressions provide a clear and concise way to implement functional interfaces.

• Example of a custom functional interface: @Functiona...read more

Java Streams provide a functional approach to processing sequences of elements, unlike Iterators which are imperative.

• Streams are part of the Java 8+ API, enabling functional-style operations on collections.

• Unlike Iterators, Streams do not store data; they process data on-the-fly.

• Streams support operations like map, filter, and reduce, allowing for concise and readable code.

• Example: List<String> names = Arrays.as...read more

Immutability in Java means objects cannot be modified after creation, enhancing security and performance.

• 1. Immutability: Once created, an object's state cannot be changed.

• 2. String Class: Strings in Java are immutable; any modification creates a new String object.

• 3. Example: String s1 = "Hello"; s1 = s1 + " World!"; // s1 now points to a new String object.

• 4. Advantages: Thread-safe, easier to cache, and can be used as...read more

final, finally, and finalize serve different purposes in Java: variable declaration, exception handling, and garbage collection respectively.

• final: Used to declare constants. Example: final int MAX_VALUE = 100;

• finally: Block that executes after try-catch, regardless of exceptions. Example: try { ... } catch { ... } finally { ... }

• finalize: Method called by the garbage collector before an object is removed. Example: pro

The Singleton pattern restricts instantiation of a class to one object, ensuring controlled access to that instance.

• 1. The Singleton pattern ensures a class has only one instance and provides a global point of access to it.

• 2. Common implementations include lazy initialization, eager initialization, and double-checked locking.

• 3. Lazy initialization: Create the instance when it is needed, using synchronized method for th...read more

Java annotations provide metadata for classes, methods, and fields, enhancing functionality in frameworks like Spring.

• Annotations are metadata that provide information about the program but are not part of the program itself.

• In Spring, annotations like @Component, @Service, and @Controller are used for defining beans and their roles.

• Built-in annotations include @Override, @Deprecated, and @SuppressWarnings, which serve...read more

Java Streams enable parallel processing for efficient data handling but come with potential pitfalls that need careful management.

• Java Streams can be processed in parallel using the 'parallelStream()' method, which divides the workload across multiple threads.

• Parallel streams utilize the Fork/Join framework, allowing tasks to be split and executed concurrently, improving performance for large datasets.

• Potential pitfall...read more

ArrayList offers fast access and is memory efficient, while LinkedList excels in insertions and deletions.

• ArrayList provides O(1) access time, making it ideal for frequent retrievals.

• LinkedList allows O(1) insertions/deletions at both ends, suitable for dynamic data structures.

• Example: Use ArrayList for a list of user names where retrieval is frequent.

• Example: Use LinkedList for a playlist where songs are frequently ad...read more

== checks reference equality; .equals() checks value equality, can be overridden for custom comparison.

• == compares memory addresses: new String("hello") == new String("hello") returns false.

• .equals() compares actual content: "hello".equals("hello") returns true.

• Override equals() when logical equality differs from reference equality, e.g., in custom classes.

• When overriding equals(), also override hashCode() to maintain ...read more

Java's garbage collector automatically manages memory, reclaiming space from unused objects through various algorithms.

• Garbage collection in Java is automatic, freeing developers from manual memory management.

• The JVM uses different GC algorithms: Serial, Parallel, CMS, and G1, each with unique characteristics.

• Memory is divided into Young Generation (short-lived objects) and Old Generation (long-lived objects).

• Minor GC ...read more

Lambda expressions enhance Java code readability and maintainability by simplifying syntax and promoting functional programming.

• Concise Syntax: Lambda expressions reduce boilerplate code. For example, instead of writing an anonymous class for a Runnable, you can use: `Runnable r = () -> System.out.println("Hello");`

• Improved Readability: Code becomes more expressive. For instance, using `list.forEach(item -> Syste...read more

ArrayList uses dynamic arrays, while LinkedList uses doubly linked nodes for storage and access.

• ArrayList provides fast random access (O(1)) due to its underlying array structure.

• LinkedList allows for efficient insertions and deletions (O(1)) at both ends, as it only requires pointer updates.

• ArrayList has a fixed size, which can lead to resizing (O(n)) when capacity is exceeded, while LinkedList grows dynamically.

• Examp...read more

In Java, '==' checks reference equality, while '.equals()' checks value equality. Use appropriately to avoid bugs.

• == compares object references (memory addresses). Example: String a = new String('test'); String b = new String('test'); a == b is false.

• .equals() compares the actual content of objects. Example: a.equals(b) is true.

• Use '==' for primitive types (int, char, etc.) and .equals() for objects.

• Improper use of '==...read more

Java's garbage collector automatically manages memory by reclaiming unused objects, optimizing performance and resource usage.

• 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 small app...read more

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

• 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 with...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 RuntimeException.

• Example: IOException is a checked exception that must be caught or declared.

• Unchecked exceptions are subclasses of RuntimeException.

• Example: NullPointerException is an unchecked exception that does not need to be declared.

• Checked exceptions e...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 between threads, preventing stale data issues.

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

• The 'volatile' ...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: '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 method nam...read more

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

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

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

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 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

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

ArrayList uses dynamic arrays, while LinkedList uses doubly linked nodes for storage and access.

• ArrayList provides fast random access (O(1)) but slow insertions/deletions (O(n)). Example: accessing elements by index.

• LinkedList allows fast insertions/deletions (O(1) at both ends) but slower random access (O(n)). Example: adding/removing elements from the front.

• ArrayList is preferred when you need frequent access to elem...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 thread contention and deadlocks.

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

• ReentrantLock can be more efficient in high-contention scenarios.

• Synchronized blocks are easier to rea

In Java, '==' checks reference equality, while '.equals()' checks value equality. Use 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 for equality.

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

• Use '==' for pri...read more

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

• Lambda Expressions: Enable concise representation of functional interfaces. Example: (a, b) -> a + b.

• 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 inte...read more

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

• Unchecked exceptions c...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 of shared variables.

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

• Synchronization mechanisms (like synchronized blocks) help prevent data rac...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

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: accessing element at index 5 is quick.

• LinkedList consists of nodes, each containing data and pointers to next/previous nodes, making insertions/removals faster (O(1)).

• ArrayList has a fixed size; resizing involves...read more

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 is not interruptible.

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

• ReentrantLock can be more flexible with lock management, allowing for multiple conditions.

In Java, '==' checks reference equality, while '.equals()' checks value equality. Use them appropriately to avoid bugs.

• == compares object references (memory addresses). Example: String a = new String('test'); String b = new String('test'); a == b is false.

• .equals() compares actual content/values of objects. Example: a.equals(b) is true.

• Use '==' for primitive types (int, char, etc.) and .equals() for objects.

• Improper us...read more

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

• Generational Garbage Collection: Divides memory into Young, Old, and Permanent generations for efficient memory management.

• Minor GC: Cleans up the Young generation, where most objects are short-lived, minimizing pause times.

• Major GC: Cleans up the Old generation, which can take longer as...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 functional interfaces. Example: (x, y) -> x + y.

• 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 impl...read more

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

• Unchecked exceptions c...read more

The Java Memory Model defines how threads interact through memory, ensuring visibility and ordering in multithreaded environments.

• The Java Memory Model (JMM) specifies how variables are read and written in a multithreaded context.

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

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

• The 'volat...read more

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 lists (type, number, or both).

• Example of Overloading: public int add(int a, int b) { return a + b; } public double add(double a, double b) { return a + b; }

• Use Case for Overloading: When you want to perform similar operations with d...read more