Question 1: What is the main responsibility of the ClassLoader subsystem?
- Execute bytecode
- Load classes into JVM memory
- Manage heap memory
- Optimize garbage collection
Explanation: ClassLoader loads class bytecode into JVM memory.
Java Quiz ( Advanced ) - All Questions
This advanced Java quiz is designed for experienced developers preparing for senior-level interviews and real-world system design discussions. It covers JVM internals, memory management, concurrency, collections internals, performance tuning, design principles, and advanced Java concepts.
Question 2: Which memory area replaced PermGen in Java 8?
- Heap
- Stack
- Metaspace
- Code Cache
Explanation: Metaspace replaced PermGen in Java 8.
Question 3: What is stored in Metaspace?
- Objects
- Thread stacks
- Class metadata
- Temporary variables
Explanation: Metaspace stores class-level metadata.
Question 4: Which garbage collector is optimized for low-latency applications?
- Serial GC
- Parallel GC
- G1 GC
- Mark and Sweep
Explanation: G1 GC focuses on predictable pause times.
Question 5: What does the volatile keyword guarantee?
- Atomicity
- Thread safety
- Visibility across threads
- Mutual exclusion
Explanation: volatile ensures visibility of variable updates.
Question 6: Which keyword ensures mutual exclusion?
- volatile
- final
- synchronized
- transient
Explanation: synchronized prevents concurrent access.
Question 7: Why is double-checked locking used in Singleton?
- Reduce memory usage
- Ensure thread safety with better performance
- Avoid garbage collection
- Prevent deadlocks
Explanation: It reduces synchronization overhead.
Question 8: Which collection is NOT thread-safe by default?
- Hashtable
- Vector
- ConcurrentHashMap
- ArrayList
Explanation: ArrayList is not synchronized.
Question 9: What issue can occur when HashMap is modified concurrently?
- Compilation error
- Deadlock
- Infinite loop during rehashing
- Automatic synchronization
Explanation: Concurrent modification can cause infinite loops.
Question 10: What is the main difference between HashMap and ConcurrentHashMap?
- Memory size
- Thread safety and locking strategy
- Iteration order
- Key uniqueness
Explanation: ConcurrentHashMap allows safe concurrent access.
Question 11: Which interface enables lambda expressions?
- Serializable
- Runnable
- FunctionalInterface
- Comparable
Explanation: Functional interfaces support lambdas.
Question 12: What is the purpose of Java Stream API?
- Thread creation
- Functional-style data processing
- File handling
- Memory management
Explanation: Streams process data in functional style.
Question 13: Which Stream operation is terminal?
- map()
- filter()
- sorted()
- collect()
Explanation: collect() terminates the stream.
Question 14: Which Stream operation transforms elements?
- filter()
- map()
- forEach()
- collect()
Explanation: map() transforms each element.
Question 15: What is the Fork/Join framework used for?
- Thread synchronization
- Parallel task execution
- Asynchronous IO
- Memory sharing
Explanation: Fork/Join enables parallelism.
Question 16: Which exception occurs when a class is missing at runtime?
- ClassNotFoundException
- NoClassDefFoundError
- IOException
- InstantiationException
Explanation: NoClassDefFoundError occurs at runtime.
Question 17: What is the key difference between Error and Exception?
- Errors are recoverable
- Exceptions stop JVM
- Errors represent serious system issues
- Exceptions are unchecked
Explanation: Errors indicate serious JVM-level problems.
Question 18: Why are immutable objects thread-safe?
- They use locks
- Their state cannot change
- They are synchronized
- They use volatile variables
Explanation: State cannot be modified after creation.
Question 19: Why are wrapper classes immutable?
- Performance
- Security and caching
- Syntax simplicity
- Serialization
Explanation: Immutability enables caching and safety.
Question 20: Which JVM optimization avoids heap allocation?
- Inlining
- Scalar replacement
- Loop unrolling
- Dead code elimination
Explanation: Scalar replacement removes object allocation.
Question 21: What is escape analysis used for?
- Security checks
- Optimizing memory allocation
- Exception handling
- Thread management
Explanation: Escape analysis optimizes object allocation.
Question 22: What is the role of the JIT compiler?
- Compile source code
- Interpret bytecode
- Optimize bytecode at runtime
- Manage heap memory
Explanation: JIT compiles bytecode into native code.
Question 23: Which reference type helps prevent memory leaks?
- Strong
- Soft
- Weak
- Phantom
Explanation: Weak references allow GC cleanup.
Question 24: Which collection is implemented using a Red-Black Tree?
- HashMap
- TreeMap
- ArrayList
- LinkedList
Explanation: TreeMap uses a Red-Black Tree.
Question 25: Why must hashCode() be overridden with equals()?
- Serialization
- Hash-based collection correctness
- Thread safety
- Performance
Explanation: HashMap relies on hashCode and equals.
Question 26: Which concurrency issue causes inconsistent results?
- Deadlock
- Starvation
- Race condition
- Livelock
Explanation: Race conditions cause inconsistent state.
Question 27: What is livelock?
- Threads blocked forever
- Threads active but not progressing
- Dead JVM
- CPU idle state
Explanation: Threads respond but make no progress.
Question 28: Which ExecutorService is best for CPU-bound tasks?
- CachedThreadPool
- SingleThreadExecutor
- FixedThreadPool
- ScheduledExecutor
Explanation: FixedThreadPool suits CPU-bound workloads.
Question 29: Why should checked exceptions be used carefully?
- Performance issues
- Increased tight coupling
- Compilation errors
- Memory overhead
Explanation: Checked exceptions increase coupling.
Question 30: What is the purpose of Serializable?
- Thread safety
- Object persistence
- Cloning objects
- Security
Explanation: Serializable allows object serialization.
Question 31: Which design pattern ensures a single instance?
- Factory
- Builder
- Singleton
- Prototype
Explanation: Singleton restricts object creation.
Question 32: Which Singleton implementation is thread-safe and lazy?
- Eager initialization
- Enum Singleton
- Synchronized method
- Double-checked locking
Explanation: Double-checked locking is lazy and efficient.
Question 33: Which SOLID principle promotes abstraction dependency?
- Single Responsibility
- Open-Closed
- Dependency Inversion
- Liskov Substitution
Explanation: DIP promotes abstraction-based design.
Question 34: Why should reflection be used cautiously?
- Syntax complexity
- Performance and security risks
- Compilation errors
- Memory leaks
Explanation: Reflection impacts performance and security.
Question 35: Which Java feature supports runtime polymorphism?
- Method overloading
- Method overriding
- Static binding
- Final methods
Explanation: Overriding enables runtime polymorphism.
Question 36: What is the primary goal of mastering Java?
- Framework usage
- Building scalable and maintainable systems
- Frontend development
- Database administration
Explanation: Java mastery enables scalable system design.
Java Quiz ( Advanced )
This advanced Java quiz is designed for experienced developers preparing for senior-level interviews and real-world system design discussions. It covers JVM internals, memory management, concurrency, collections internals, performance tuning, design principles, and advanced Java concepts.
15
Questions
~8
Minutes
8
Min Limit