21 Functional questions from the Java bank, written for Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd.
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A.a stream intermediate operation that transforms each element by applying a function, producing a new stream
B.a container object that may or may not hold a non-null value, used to avoid null reference errors
C.an interface with exactly one abstract method, eligible to be implemented by a lambda or method reference
D.a concise anonymous function written with arrow syntax that implements a functional interface
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2. Which term means: "a concise anonymous function written with arrow syntax that implements a functional interface"?
Junior
A.Functional interface
B.Stream
C.Lambda expression
D.collect operation
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3. Which statement is correct?
Junior
A.Lambda expression — a concise anonymous function written with arrow syntax that implements a functional interface
B.Lambda expression — an interface with exactly one abstract method, eligible to be implemented by a lambda or method reference
C.Lambda expression — a lazily-evaluated pipeline for processing a sequence of elements with operations like filter and map
D.Lambda expression — a container object that may or may not hold a non-null value, used to avoid null reference errors
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4. What is Functional interface?
Mid
A.a concise anonymous function written with arrow syntax that implements a functional interface
B.a container object that may or may not hold a non-null value, used to avoid null reference errors
C.an interface with exactly one abstract method, eligible to be implemented by a lambda or method reference
D.a stream intermediate operation that keeps only the elements matching a given predicate
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5. Which term means: "an interface with exactly one abstract method, eligible to be implemented by a lambda or method reference"?
Mid
A.Optional
B.filter operation
C.collect operation
D.Functional interface
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6. Which statement is correct?
Mid
A.Functional interface — a stream terminal operation that accumulates elements into a result container such as a list or map using a Collector
B.Functional interface — an interface with exactly one abstract method, eligible to be implemented by a lambda or method reference
C.Functional interface — a lazily-evaluated pipeline for processing a sequence of elements with operations like filter and map
D.Functional interface — a container object that may or may not hold a non-null value, used to avoid null reference errors
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7. What is Stream?
Junior
A.a concise anonymous function written with arrow syntax that implements a functional interface
B.a stream terminal operation that accumulates elements into a result container such as a list or map using a Collector
C.a stream intermediate operation that transforms each element by applying a function, producing a new stream
D.a lazily-evaluated pipeline for processing a sequence of elements with operations like filter and map
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8. Which term means: "a lazily-evaluated pipeline for processing a sequence of elements with operations like filter and map"?
Junior
A.Stream
B.Lambda expression
C.collect operation
D.map operation
Answer + AI explanation with Pro
9. Which statement is correct?
Junior
A.Stream — a lazily-evaluated pipeline for processing a sequence of elements with operations like filter and map
B.Stream — a concise anonymous function written with arrow syntax that implements a functional interface
C.Stream — an interface with exactly one abstract method, eligible to be implemented by a lambda or method reference
D.Stream — a stream intermediate operation that transforms each element by applying a function, producing a new stream
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10. What is map operation?
Mid
A.a stream terminal operation that accumulates elements into a result container such as a list or map using a Collector
B.a container object that may or may not hold a non-null value, used to avoid null reference errors
C.a stream intermediate operation that transforms each element by applying a function, producing a new stream
D.an interface with exactly one abstract method, eligible to be implemented by a lambda or method reference
Answer + AI explanation with Pro
11. Which term means: "a stream intermediate operation that transforms each element by applying a function, producing a new stream"?
Mid
A.Optional
B.collect operation
C.Functional interface
D.map operation
Answer + AI explanation with Pro
12. Which statement is correct?
Mid
A.map operation — a stream terminal operation that accumulates elements into a result container such as a list or map using a Collector
B.map operation — a container object that may or may not hold a non-null value, used to avoid null reference errors
C.map operation — a stream intermediate operation that transforms each element by applying a function, producing a new stream
D.map operation — a lazily-evaluated pipeline for processing a sequence of elements with operations like filter and map
Answer + AI explanation with Pro
13. What is filter operation?
Mid
A.a stream intermediate operation that transforms each element by applying a function, producing a new stream
B.a stream intermediate operation that keeps only the elements matching a given predicate
C.a container object that may or may not hold a non-null value, used to avoid null reference errors
D.an interface with exactly one abstract method, eligible to be implemented by a lambda or method reference
Answer + AI explanation with Pro
14. Which term means: "a stream intermediate operation that keeps only the elements matching a given predicate"?
Mid
A.filter operation
B.Functional interface
C.collect operation
D.Optional
Answer + AI explanation with Pro
15. Which statement is correct?
Mid
A.filter operation — a lazily-evaluated pipeline for processing a sequence of elements with operations like filter and map
B.filter operation — a concise anonymous function written with arrow syntax that implements a functional interface
C.filter operation — a stream terminal operation that accumulates elements into a result container such as a list or map using a Collector
D.filter operation — a stream intermediate operation that keeps only the elements matching a given predicate
Answer + AI explanation with Pro
16. What is collect operation?
Senior
A.a stream terminal operation that accumulates elements into a result container such as a list or map using a Collector
B.a concise anonymous function written with arrow syntax that implements a functional interface
C.a stream intermediate operation that transforms each element by applying a function, producing a new stream
D.an interface with exactly one abstract method, eligible to be implemented by a lambda or method reference
Answer + AI explanation with Pro
17. Which term means: "a stream terminal operation that accumulates elements into a result container such as a list or map using a Collector"?
Senior
A.Lambda expression
B.filter operation
C.collect operation
D.Stream
Answer + AI explanation with Pro
18. Which statement is correct?
Senior
A.collect operation — a stream terminal operation that accumulates elements into a result container such as a list or map using a Collector
B.collect operation — a stream intermediate operation that keeps only the elements matching a given predicate
C.collect operation — a concise anonymous function written with arrow syntax that implements a functional interface
D.collect operation — a container object that may or may not hold a non-null value, used to avoid null reference errors
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19. What is Optional?
Senior
A.a stream terminal operation that accumulates elements into a result container such as a list or map using a Collector
B.a container object that may or may not hold a non-null value, used to avoid null reference errors
C.a concise anonymous function written with arrow syntax that implements a functional interface
D.a lazily-evaluated pipeline for processing a sequence of elements with operations like filter and map
Answer + AI explanation with Pro
20. Which term means: "a container object that may or may not hold a non-null value, used to avoid null reference errors"?
Senior
A.collect operation
B.Lambda expression
C.filter operation
D.Optional
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21. Which statement is correct?
Senior
A.Optional — a concise anonymous function written with arrow syntax that implements a functional interface
B.Optional — a container object that may or may not hold a non-null value, used to avoid null reference errors
C.Optional — a stream intermediate operation that keeps only the elements matching a given predicate
D.Optional — an interface with exactly one abstract method, eligible to be implemented by a lambda or method reference
Answer + AI explanation with Pro
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