The same remarks apply as for “Refactoring the Traditional for Loop”
- No init()
- Negative tests which apply for input less than 1900, resulting in exceptions.
but we cannot implement a common interface as the method parameters change. So we wrap the new class into a class that obeys the old interface, which agains llaows us to use the same test code to test both odl and new classes.
There is also a little tweak to the semantics of the case where 1900 is already rejected - instead of returning 0, we throw. Because there basically is no result in that case.
package chapter11;
import org.junit.jupiter.api.Test;
import java.time.Year;
import java.util.function.Predicate;
import java.util.stream.IntStream;
import static org.junit.jupiter.api.Assertions.*;
public class UnboundedLoopTest {
interface Continue {
boolean check(int year);
}
interface WithContinue {
int countFrom1900(final Continue shouldContinue);
}
static class LeapYearsUnboundedBefore implements WithContinue {
public int countFrom1900(final Continue shouldContinue) {
if (!shouldContinue.check(1900)) {
throw new IllegalArgumentException("Cannot 'continue' right at the start!'");
}
int count = 0;
for (int year = 1900; ; year += 4) {
if (!shouldContinue.check(year)) {
break;
}
if (Year.isLeap(year)) {
count++;
}
}
return count;
}
}
// Does NOT implement WithContinue!!
static class LeapYearsUnboundedAfter {
public int countFrom1900(final Predicate<Integer> shouldContinue) {
if (!shouldContinue.test(1900)) {
throw new IllegalArgumentException("Cannot 'continue' right at the start!'");
}
return (int) IntStream.iterate(1900, year -> year + 4)
.takeWhile(shouldContinue::test)
.filter(Year::isLeap)
.count();
}
}
static class LeapYearsUnboundedAfterWrapped implements WithContinue {
private final LeapYearsUnboundedAfter ly;
public LeapYearsUnboundedAfterWrapped(LeapYearsUnboundedAfter ly) {
this.ly = ly;
}
public int countFrom1900(final Continue shouldContinue) {
return ly.countFrom1900(year -> shouldContinue.check(year));
}
}
// One should maybe have a separate method to test the throws
private static void commonLeapYearsTests(final WithContinue withContinue) {
assertAll(
() -> assertEquals(0, withContinue.countFrom1900(year -> year <= 1900)),
() -> assertEquals(25, withContinue.countFrom1900(year -> year <= 2000)),
() -> assertEquals(27, withContinue.countFrom1900(year -> year <= 2010)),
() -> assertEquals(31, withContinue.countFrom1900(year -> year <= 2025)),
() -> assertEquals(49, withContinue.countFrom1900(year -> year <= 2100)),
() -> assertEquals(267, withContinue.countFrom1900(year -> year <= 3000)),
() -> assertThrows(IllegalArgumentException.class, () ->
withContinue.countFrom1900(year -> year < 1800)
),
() -> assertThrows(IllegalArgumentException.class, () ->
withContinue.countFrom1900(year -> year < 1900)
)
);
}
@Test
void leapYearCountBefore() {
commonLeapYearsTests(new LeapYearsUnboundedBefore());
}
@Test
void leapYearCountAfter() {
commonLeapYearsTests(new LeapYearsUnboundedAfterWrapped(new LeapYearsUnboundedAfter()));
}
}