BAEL-949 java9 optional test (#1960)
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package com.baeldung.java9;
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public class Java9OptionalTest {
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@Test
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public void givenOptionalOfSome_whenToStream_thenShouldTreatItAsOneElementStream() {
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//given
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Optional<String> value = Optional.of("a");
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//when
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List<String> collect = value.stream().map(String::toUpperCase).collect(Collectors.toList());
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//then
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assertThat(collect).hasSameElementsAs(List.of("A"));
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}
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@Test
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public void givenOptionalOfNone_whenToStream_thenShouldTreatItAsZeroElementStream() {
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//given
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Optional<String> value = Optional.empty();
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//when
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List<String> collect = value.stream().map(String::toUpperCase).collect(Collectors.toList());
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//then
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assertThat(collect).isEmpty();
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}
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@Test
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public void givenOptional_whenPresent_thenShouldExecuteProperCallback() {
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//given
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Optional<String> value = Optional.of("properValue");
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AtomicInteger successCounter = new AtomicInteger(0);
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AtomicInteger onEmptyOptionalCounter = new AtomicInteger(0);
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//when
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value.ifPresentOrElse((v) -> successCounter.incrementAndGet(), onEmptyOptionalCounter::incrementAndGet);
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//then
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assertThat(successCounter.get()).isEqualTo(1);
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assertThat(onEmptyOptionalCounter.get()).isEqualTo(0);
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}
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@Test
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public void givenOptional_whenNotPresent_thenShouldExecuteProperCallback() {
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//given
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Optional<String> value = Optional.empty();
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AtomicInteger successCounter = new AtomicInteger(0);
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AtomicInteger onEmptyOptionalCounter = new AtomicInteger(0);
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//when
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value.ifPresentOrElse((v) -> successCounter.incrementAndGet(), onEmptyOptionalCounter::incrementAndGet);
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//then
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assertThat(successCounter.get()).isEqualTo(0);
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assertThat(onEmptyOptionalCounter.get()).isEqualTo(1);
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}
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@Test
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public void givenOptional_whenPresent_thenShouldTakeAValueFromIt() {
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//given
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String expected = "properValue";
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Optional<String> value = Optional.of(expected);
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Optional<String> defaultValue = Optional.of("default");
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//when
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Optional<String> result = value.or(() -> defaultValue);
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//then
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assertThat(result.get()).isEqualTo(expected);
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}
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@Test
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public void givenOptional_whenEmpty_thenShouldTakeAValueFromOr() {
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//given
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String defaultString = "default";
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Optional<String> value = Optional.empty();
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Optional<String> defaultValue = Optional.of(defaultString);
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//when
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Optional<String> result = value.or(() -> defaultValue);
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//then
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assertThat(result.get()).isEqualTo(defaultString);
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}
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}
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