Functional Programming in Java, Second Edition: Code for "Chapter 7, Lazy Evaluations" in one file

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package chapter7;

import org.junit.jupiter.api.Test;

import java.util.List;
import java.util.function.Supplier;
import java.util.stream.Stream;

public class BeingLazy_LazyEvaluations {

    private final static List<String> names = List.of("Brad", "Kate", "Kim", "Jack", "Joe", "Mike", "Susan", "George", "Robert", "Julia", "Parker", "Benson");
    
    // "lazy/fpij/Evaluation.java" on p. 127, p.128

    private static boolean evaluate(final int value) {
        System.out.println("evaluating ..." + value);
        simulateTimeConsumingOp(2000);
        return value > 100;
    }

    private static void simulateTimeConsumingOp(long time_ms) {
        try {
            Thread.sleep(time_ms);
        } catch (InterruptedException ex) {
            throw new RuntimeException(ex);
        }
    }

    // "lazy/fpij/Evaluation.java" p. 127

    private static void eagerEvaluator(final boolean input1, final boolean input2) {
        System.out.println("eagerEvaluator called...");
        System.out.println("accept?: " + (input1 && input2));
    }

    // "lazy/fpij/Evaluation.java" p. 128

    private static void lazyEvaluator(final Supplier<Boolean> input1, final Supplier<Boolean> input2) {
        System.out.println("lazyEvaluator called...");
        System.out.println("accept?: " + (input1.get() && input2.get()));
    }

    // "lazy/fpij/LazyStreams.java" on p.130

    private static int length(final String name) {
        System.out.println("getting length for " + name);
        return name.length();
    }

    // "lazy/fpij/LazyStreams.java" on p.130

    private static String toUpper(final String name) {
        System.out.println("converting to uppercase: " + name);
        return name.toUpperCase();
    }

    // "lazy/fpij/Evaluation.java" on p.127

    @Test
    void evaluateEagerly() {
        eagerEvaluator(evaluate(1), evaluate(2));
    }

    // "lazy/fpij/Evaluation.java" on p.128

    @Test
    void evaluateLazily() {
        lazyEvaluator(() -> evaluate(1), () -> evaluate(2));
    }

    // "lazy/fpij/LazyStreams.java" on p.130
    // ".map(name -> toUpper(name))" replaced with ".map(LazyStreams::toUpper)"

    @Test
    void lazyStream() {
        final String firstNameWith3Letters =
                names.stream()
                        .filter(name -> length(name) == 3)
                        .map(BeingLazy_LazyEvaluations::toUpper)
                        .findFirst()
                        .orElse("");
        System.out.println(firstNameWith3Letters);
    }

    // lazy/fpij/LazyStreams.java on p.132
    // ".map(name -> toUpper(name))" replaced with ".map(LazyStreams::toUpper)"

    @Test
    void peekingIntoLaziness() {
        Stream<String> namesWith3Letters =
                names.stream()
                        .filter(name -> length(name) == 3)
                        .map(BeingLazy_LazyEvaluations::toUpper);
        System.out.println("Stream created, filtered, mapped...");
        System.out.println("ready to call findFirst...");
        final String firstNameWith3Letters =
                namesWith3Letters
                        .findFirst()
                        .orElse("");
        System.out.println(firstNameWith3Letters);
    }

}