Concurrency & Threads interview questions

18 real Concurrency & Threads questions from the Java bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.

1. What is Thread?

Junior
  1. A.a state where two or more threads are blocked forever, each waiting for a lock the other holds
  2. B.an abstraction that manages a pool of worker threads and accepts tasks for asynchronous execution
  3. C.a field modifier that guarantees reads and writes go directly to main memory, ensuring visibility across threads without locking
  4. D.an independent path of execution within a program that the JVM can schedule to run concurrently
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3. Which statement is correct?

Junior
  1. A.Thread — a functional interface whose run method holds the code a thread executes, returning no result
  2. B.Thread — a field modifier that guarantees reads and writes go directly to main memory, ensuring visibility across threads without locking
  3. C.Thread — an independent path of execution within a program that the JVM can schedule to run concurrently
  4. D.Thread — a state where two or more threads are blocked forever, each waiting for a lock the other holds
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4. What is synchronized keyword?

Mid
  1. A.a modifier that acquires an object monitor lock so only one thread at a time executes the guarded block or method
  2. B.a functional interface whose run method holds the code a thread executes, returning no result
  3. C.an abstraction that manages a pool of worker threads and accepts tasks for asynchronous execution
  4. D.an independent path of execution within a program that the JVM can schedule to run concurrently
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6. Which statement is correct?

Mid
  1. A.synchronized keyword — an abstraction that manages a pool of worker threads and accepts tasks for asynchronous execution
  2. B.synchronized keyword — a modifier that acquires an object monitor lock so only one thread at a time executes the guarded block or method
  3. C.synchronized keyword — an independent path of execution within a program that the JVM can schedule to run concurrently
  4. D.synchronized keyword — a state where two or more threads are blocked forever, each waiting for a lock the other holds
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7. What is volatile keyword?

Mid
  1. A.an independent path of execution within a program that the JVM can schedule to run concurrently
  2. B.a modifier that acquires an object monitor lock so only one thread at a time executes the guarded block or method
  3. C.an abstraction that manages a pool of worker threads and accepts tasks for asynchronous execution
  4. D.a field modifier that guarantees reads and writes go directly to main memory, ensuring visibility across threads without locking
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8. Which term means: "a field modifier that guarantees reads and writes go directly to main memory, ensuring visibility across threads without locking"?

Mid
  1. A.Deadlock
  2. B.volatile keyword
  3. C.synchronized keyword
  4. D.ExecutorService
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9. Which statement is correct?

Mid
  1. A.volatile keyword — a functional interface whose run method holds the code a thread executes, returning no result
  2. B.volatile keyword — a field modifier that guarantees reads and writes go directly to main memory, ensuring visibility across threads without locking
  3. C.volatile keyword — an independent path of execution within a program that the JVM can schedule to run concurrently
  4. D.volatile keyword — a modifier that acquires an object monitor lock so only one thread at a time executes the guarded block or method
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10. What is Deadlock?

Senior
  1. A.a field modifier that guarantees reads and writes go directly to main memory, ensuring visibility across threads without locking
  2. B.a state where two or more threads are blocked forever, each waiting for a lock the other holds
  3. C.an abstraction that manages a pool of worker threads and accepts tasks for asynchronous execution
  4. D.an independent path of execution within a program that the JVM can schedule to run concurrently
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12. Which statement is correct?

Senior
  1. A.Deadlock — a modifier that acquires an object monitor lock so only one thread at a time executes the guarded block or method
  2. B.Deadlock — an independent path of execution within a program that the JVM can schedule to run concurrently
  3. C.Deadlock — an abstraction that manages a pool of worker threads and accepts tasks for asynchronous execution
  4. D.Deadlock — a state where two or more threads are blocked forever, each waiting for a lock the other holds
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13. What is ExecutorService?

Senior
  1. A.a field modifier that guarantees reads and writes go directly to main memory, ensuring visibility across threads without locking
  2. B.an abstraction that manages a pool of worker threads and accepts tasks for asynchronous execution
  3. C.an independent path of execution within a program that the JVM can schedule to run concurrently
  4. D.a modifier that acquires an object monitor lock so only one thread at a time executes the guarded block or method
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15. Which statement is correct?

Senior
  1. A.ExecutorService — a state where two or more threads are blocked forever, each waiting for a lock the other holds
  2. B.ExecutorService — a modifier that acquires an object monitor lock so only one thread at a time executes the guarded block or method
  3. C.ExecutorService — a field modifier that guarantees reads and writes go directly to main memory, ensuring visibility across threads without locking
  4. D.ExecutorService — an abstraction that manages a pool of worker threads and accepts tasks for asynchronous execution
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16. What is Runnable?

Mid
  1. A.a functional interface whose run method holds the code a thread executes, returning no result
  2. B.an abstraction that manages a pool of worker threads and accepts tasks for asynchronous execution
  3. C.a field modifier that guarantees reads and writes go directly to main memory, ensuring visibility across threads without locking
  4. D.a state where two or more threads are blocked forever, each waiting for a lock the other holds
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18. Which statement is correct?

Mid
  1. A.Runnable — an independent path of execution within a program that the JVM can schedule to run concurrently
  2. B.Runnable — a modifier that acquires an object monitor lock so only one thread at a time executes the guarded block or method
  3. C.Runnable — a functional interface whose run method holds the code a thread executes, returning no result
  4. D.Runnable — a field modifier that guarantees reads and writes go directly to main memory, ensuring visibility across threads without locking
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