Composing Functions – Quiz

Java 11 Certification Practice Questions (Answers below)

Section: Working with Streams and Lambda expressions

Objective: Implement functional interfaces using lambda expressions, including interfaces from the java.util.function package

Q1. What will be the result?

	Function<Integer, Integer> x = a -> a * 5;
	Function<Integer, Integer> y = a -> a % 5;
	Function<Integer, Integer> z = x.compose(y);
	System.out.println(z.apply(12));

Choices

A. The code does not compile
B. Prints 0
C. Prints 10

Answers

Q1. C is the correct answer.

The x.compose(y) method calls the Function parameter y before the reference
Function variable x. Hence, first 12 % 5 is done which gives 2. Then 2 is multiplied by 5 which gives 10 as the output.

Reference

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