Programming Languages Chapter 30 Aggregate Operations Collection Streams Section Stream Pipelines The Default Method Defined

Chapter 30 Aggregate Operations on Collection Streams

Section 30.2 Stream Pipelines

1. The default method is defined the Collection interface for creating a stream.

a. getStream()

b. Stream()

c. stream()

d. findStream()

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2. The Stream interface extends .

a. Collection

b. Collections

c. BaseStreams

d. BaseStream

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3. A stream pipeline may contain intermediate methods.

a. 0

b. 1

c. 0 or 1

d. 0 or more

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4. A stream pipeline may contain terminal methods.

a. 0

b. 1

c. 0 or 1

d. 0 or more

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5. The Stream<T> interface contains static methods for creating instances of Stream.

a. empty()

b. of(T… values)

c. of(values: T)

d. concat(Stream<? extedns T> s1, Stream<? extends T> s2)

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6. is an intermediate method.

a. distinct

b. filter

c. limit

d. skip

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7. is an intermediate method.

a. sorted

b. map

c. mapToInt

d. mapToLong

e. mapToDouble

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8. is a terminal method.

a. count

b. max

c. min

d. findFirst

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9. is a terminal method.

a. allMatch

b. anyMatch

c. noneMatch

d. forEach

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10. is a terminal method.

a. reduce

b. collect

c. toArray

d. map

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11. Which of the following methods takes an argument of the Comparator type?

a. max

b. min

c. sorted

d. forEach

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12. The statement forEach(System.out::println) is the same as .

a. forEach(System.out::print)

b. forEach(System.out.println)

c. forEach(e –> System.out.println())

d. forEach(e –> System.out.println(e))

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13. The statement sorted((s1, s2) –> s1.compareToIgnoreCase(s2)) is the same as .

a. sorted(String::compareToIgnoreCase(s))

b. sorted(String::compareToIgnoreCase())

c. sorted(String::compareToIgnoreCase)

d. sorted(compareToIgnoreCase(s))

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14. What is the output of the following code?

Character[] chars = {‘D’, ‘B’, ‘A’, ‘C’};

Stream.of(chars).filter(e –> e > ‘B’).sorted()

.forEach(System.out::print);

a. DC

b. CD

c. ABCD

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15. What is the output of the following code?

Character[] chars = {‘D’, ‘B’, ‘A’, ‘C’};

System.out.println(Stream.of(chars).allMatch(e –> e > ‘B’) + ” ” +

Stream.of(chars).noneMatch(e –> e > ‘B’));

a. true true

b. true false

c. false true

d. false false

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16. What is the output of the following code?

Character[] chars = {‘D’, ‘B’, ‘A’, ‘C’};

System.out.println(Stream.of(chars).skip(2)

.max(Character::compareTo) + “ ” +

Stream.of(chars).skip(2)

.min(Character::compareTo));

a. C C

b. A A

c. A C

d. C A

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17. What is the output of the following code?

Character[] chars = {‘D’, ‘B’, ‘A’, ‘C’};

Stream.of(chars).map(e –> e.toLowerCase()).forEach(System.out::print);

a. D B A C

b. d b a c

c. DBAC

d. dbac

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17. What is the output of the following code?

System.out.println(Stream.of(new Loan(2.5, 1, 10.0),

new Loan(7.5, 5, 10.1), new Loan(7.5, 3, 10.2),

new Loan(7.5, 3, 10.3))

.max((e1, e2) –> e1.getNumberOfYears() – e2.getNumberOfYears())

.get().getLoanAmount());

a. 10.0

b. 10.1

c. 10.2

d. 10.3

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Section 30.3 IntStream, LongStream, and DoubleStream

18. is a subtype of BaseStream.

a. Stream

b. IntStream

c. LongStream

d. DoubleStream

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19. represents a sequence of values.

a. IntStream, int

b. LongStream, long

c. DoubleStream, double

d. FloatStream, float

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20. sum() is a method defined in .

a. Stream

b. IntStream

c. LongStream

d. DoubleStream

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21. What is the output of the following code?

Character[] chars = {‘D’, ‘B’, ‘A’, ‘C’};

System.out.println(Stream.of(chars).mapToInt(e –> e – ‘A’).sum());

a. 4

b. 5

c. 6

d. 7

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22. What is the output of the following code?

double[] numbers = {1.2, 1, 2.2, 3.6};

System.out.println(DoubleStream.of(numbers)

.mapToInt(e –> (int)e).sum());

a. 4

b. 5

c. 6

d. 7

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23. What is the output of the following code?

double[] numbers = {1.2, 1.23, 2.2, 3.6};

System.out.println(DoubleStream.of(numbers)

.mapToObj(e –> e + “”).mapToInt(e –> e.length()).sum());

a. 12

b. 13

c. 14

d. 15

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Section 30.4 Parallel Streams

24. To create a parallel stream from a Collection object c, use .

a. c.stream()

b. c.parallelStream()

c. c.stream().parallel()

d. c.stream().sequential()

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25. The following statement displays .

IntStream.of(1, 2, 3, 4, 5).parallel()

.forEach(e –> System.out.print(e + ” “));

a. 1 2 3 4 5

b. 5 4 3 2 1

c. 1 2 3 5 4

d. 1 2 3 4 5 in a random order

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26. is a stateless method.

a. sorted

b. filter

c. limit

d. map

e. distinct

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27. is a stateful method.

a. sorted

b. filter

c. limit

d. map

e. distinct

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28. The following statement displays .

System.out.println(IntStream.of(1, 2, 3, 4, 5).parallel()

.reduce(0, (e1, e2) –> e1 + e2));

a. 14

b. 15

c. 16

d. 17

e. 18

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29. The following statement displays .

System.out.println(IntStream.of(1, 2, 3, 4, 5).parallel()

.reduce(1, (e1, e2) –> e1 * e2));

a. 120

b. 140

c. 130

d. 150

e. 170

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30. The following statement displays .

System.out.println(IntStream.of(1, 2, 3, 4, 5).parallel()

.reduce(Integer.MAX_VALUE, (e1, e2) –> Math.min(e1, e2)));

a. 1

b. 2

c. 3

d. 4

e. 5

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31. The following statement displays .

System.out.println(IntStream.of(1, 2, 3, 4, 5)

.mapToObj(e –> e + “”).reduce((e1, e2) –> e1 + ” ” + e2).get());

a. nothing

b. 1

c. 2

d. 3

e. 1 2 3 4 5

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32. The following statement displays .

System.out.println(IntStream.of(1, 2, 3, 4, 5)

.mapToObj(e –> e + “”).reduce((e1, e2) –> e1 + ” ” + e2).get());

a. nothing

b. 1

c. 2

d. 3

e. 1 2 3 4 5

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34. Show the output of the following code:

import java.util.stream.IntStream;

import java.util.stream.Stream;

public class Test {

public static void main(String [] args){

int[][] m = {{1, 2, 3}, {3, 4, 5}, {5, 2}, {1, 3}};

Stream.of(m).map(e –> IntStream.of(e))

.reduce((e1, e2) –> IntStream.concat(e1, e2))

.get().distinct()

.forEach(e –> System.out.print(e + ” “));

}

a. 1 2 3 3 4 5 5 2 1 2

b. 1 2 3 4 5

c. 1 2 3 4 5 in a random order

d. 5 4 3 2 1

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35. Show the output of the following code:

import java.util.stream.IntStream;

import java.util.stream.Stream;

public class Test {

public static void main(String [] args){

int[][] m = {{1, 2, 3}, {3, 4, 5}, {5, 2}, {1, 3}};

System.out.println(

Stream.of(m).map(e –> IntStream.of(e))

.reduce((e1, e2) –> IntStream.concat(e1, e2))

.get().distinct().mapToObj(e –> e + “”)

.reduce((e1, e2) –> e1 + “, ” + e2).get());

}

a. 1, 2, 3, 3, 4, 5, 5, 2, 1, 2

b. 1, 2, 3, 3, 4, 5, 5, 2, 1, 2,

c. 1, 2, 3, 4, 5,

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Section 30.6 Stream Reduction Using the collect Method

36. The following statement displays .

System.out.println(IntStream.of(1, 2, 3, 4, 5)

.collect(() –> new ArrayList(), (c, e) –> c.add(e),

(c1, c2) –> c1.addAll(c2)));

a. [1, 2, 3, 4]

b. [1]

c. [1, 2]

d. [1, 2, 3]

e. [1, 2, 3, 4, 5]

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37. The following statement displays .

System.out.println(IntStream.of(2, 5, 5, 4, 5)

.collect(() –> new TreeSet(), (c, e) –> c.add(e),

(c1, c2) –> c1.addAll(c2)));

a. [2, 4, 5, 5]

b. [2, 5, 4]

c. [2, 5, 5, 4, 5]

d. [5, 2, 4]

e. [2, 4, 5]

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37. The following statement displays .

System.out.println(IntStream.of(2, 5, 5, 4, 5)

.mapToObj(e –> e).collect(Collectors.toList()));

a. [2, 4, 5, 5]

b. [2, 5, 4]

c. [2, 5, 5, 4, 5]

d. [5, 2, 4]

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38. The following statement displays .

IntStream.of(2, 5, 5, 4, 5)

.mapToObj(e –> e).collect(Collectors.toSet())

.stream().sorted().forEach(e –> System.out.print(e + ” “));

a. 2 4 5 5

b. 2 5 4

c. 2 5 5 4 5

d. 5 2 4

e. 2 4 5

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Section 30.7 Grouping Elements Using the groupingby Collector

39. The following statement displays .

IntStream.of(1, 2, 3, 4, 1, 3, 5, 4, 4).mapToObj(e –> e).collect(

Collectors.groupingBy(e –> e, Collectors.counting()))

.forEach((k, v) –> {if (k == 3) System.out.println(k + ” ” + v);});

a. 3 1

b. 3 2

c. 3 3

d. 2 3

e. 2 1

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42. The following statement displays .

IntStream.of(1, 2, 2, 1, 1).mapToObj(e –> e).collect(

Collectors.groupingBy(e –> e, TreeMap::new, Collectors.counting()))

.forEach((k, v) –> {System.out.print(k + ” ” + v + ” “);});

a. 1 3 2 3

b. 1 3 2 1

c. 1 3 2 2

d. 2 3 1 3

e. 2 2 1 3

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42. The following statement displays .

Map<Double, Double> map = Stream.of(new Loan(2.5, 1, 10.0),

new Loan(7.5, 5, 10.1), new Loan(7.5, 3, 10.2),

new Loan(7.5, 5, 10.3))

.collect(Collectors.groupingBy(Loan::getAnnualInterestRate,

TreeMap::new,

Collectors.summingDouble(Loan::getLoanAmount)));

map.forEach((k, v) –> System.out.print(k + ” ” + v + ” “));a. 1 3 2 3

a. 7.5 10.0 2.5 30.6

b. 7.5 30.6 2.5 10.0

c. 2.5 7.5 2.5 30.6

d. 2.5 10.0 7.5 30.6

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30. Show the output of the following code.

String s = “good”;

Stream.of(s).forEach(e –>

System.out.print(e + ” “));

a. g o o d

b. good

c. a random object reference

d. [g, o, o, d]

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44. Show the output of the following code.

String s = “good”;

Stream.of(s.toCharArray()).forEach(e –>

System.out.print(e + ” “));

a. g o o d

b. good

c. a random object reference

d. [g, o, o, d]

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45. Show the output of the following code.

import java.util.stream.Stream;

public class Test {

public static void main(String[] args) {

String s = “good”;

Stream.of(toCharacterArray(s.toCharArray())).forEach(e –>

System.out.print(e + ” “));

}

public static Character[] toCharacterArray(char[] list) {

Character[] result = new Character[list.length];

for (int i = 0; i < result.length; i++) {

result[i] = list[i];

}

return result;

}

a. g o o d

b. good

c. a random object reference

d. [g, o, o, d]

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40. is a terminal method.

a. reduce

b. collect

c. forEach

d. map

e. mapToInt

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41. The forEach method is defined in the interface.

a. Stream

b. IntStream

c. LongStream

d. DoubleStream