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Use Comparable instead of dedicated implementations #25478

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Use Comparable instead of dedicated implementations #25478

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ce5d708
minor code clean-up
wind57 Jul 27, 2020
36f21bf
removed useless spaces
wind57 Jul 27, 2020
add53a8
more changes
wind57 Jul 27, 2020
8fcd878
checkstyle changes + minor refactor of tests
wind57 Jul 27, 2020
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8 changes: 5 additions & 3 deletions spring-core/src/main/java/org/springframework/util/comparator/BooleanComparator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@
* {@code true} or {@code false} first.
*
* @author Keith Donald
* @author Eugene Rabii
* @since 1.2.2
*/
@SuppressWarnings("serial")
Expand Down Expand Up @@ -63,8 +64,9 @@ public BooleanComparator(boolean trueLow) {


@Override
public int compare(Boolean v1, Boolean v2) {
return (v1 ^ v2) ? ((v1 ^ this.trueLow) ? 1 : -1) : 0;
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some time ago I had an answer about this here : https://stackoverflow.com/questions/55598277/is-there-a-useful-difference-between-p-q-and-p-q-for-booleans/55601399#55601399 and it turns out that the performance of XOR vs plain != is same. This also makes it far easier to read

public int compare(Boolean left, Boolean right) {
int multiplier = trueLow ? -1 : 1;
return multiplier * Boolean.compare(left, right);
}


Expand All @@ -76,7 +78,7 @@ public boolean equals(@Nullable Object other) {

@Override
public int hashCode() {
return getClass().hashCode() * (this.trueLow ? -1 : 1);
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since java-8 there is a way to get the hashCode without calling into getClass

return Boolean.hashCode(trueLow);
}

@Override
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9 changes: 5 additions & 4 deletions spring-core/src/test/java/org/springframework/util/comparator/BooleanComparatorTests.java
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Expand Up @@ -29,34 +29,35 @@
* @author Keith Donald
* @author Chris Beams
* @author Phillip Webb
* @author Eugene Rabii
*/
class BooleanComparatorTests {

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tests have changed because the documentation of Boolean::compare does not guarantee -1, 0, 1; but it does less than 1, 0, greater than 1

@Test
void shouldCompareWithTrueLow() {
Comparator<Boolean> c = new BooleanComparator(true);
assertThat(c.compare(true, false)).isEqualTo(-1);
assertThat(c.compare(true, false)).isLessThan(0);
assertThat(c.compare(Boolean.TRUE, Boolean.TRUE)).isEqualTo(0);
}

@Test
void shouldCompareWithTrueHigh() {
Comparator<Boolean> c = new BooleanComparator(false);
assertThat(c.compare(true, false)).isEqualTo(1);
assertThat(c.compare(true, false)).isGreaterThan(0);
assertThat(c.compare(Boolean.TRUE, Boolean.TRUE)).isEqualTo(0);
}

@Test
void shouldCompareFromTrueLow() {
Comparator<Boolean> c = BooleanComparator.TRUE_LOW;
assertThat(c.compare(true, false)).isEqualTo(-1);
assertThat(c.compare(true, false)).isLessThan(0);
assertThat(c.compare(Boolean.TRUE, Boolean.TRUE)).isEqualTo(0);
}

@Test
void shouldCompareFromTrueHigh() {
Comparator<Boolean> c = BooleanComparator.TRUE_HIGH;
assertThat(c.compare(true, false)).isEqualTo(1);
assertThat(c.compare(true, false)).isGreaterThan(0);
assertThat(c.compare(Boolean.TRUE, Boolean.TRUE)).isEqualTo(0);
}

Expand Down