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52 changes: 38 additions & 14 deletions src/test/java/lambda/part3/exercise/Mapping.java
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Original file line number Diff line number Diff line change
Expand Up @@ -32,8 +32,11 @@ public List<T> getList() {
// [T] -> (T -> R) -> [R]
// [T1, T2, T3] -> (T -> R) -> [R1, R2, R3]
public <R> MapHelper<R> map(Function<T, R> f) {
// TODO
throw new UnsupportedOperationException();
final List<R> result = new ArrayList<>();
for (T element : list) {
result.add(f.apply(element));
}
return new MapHelper<>(result);
}

// [T] -> (T -> [R]) -> [R]
Expand Down Expand Up @@ -76,11 +79,9 @@ public void mapping() {

final List<Employee> mappedEmployees =
new MapHelper<>(employees)
/*
.map(TODO) // change name to John .map(e -> e.withPerson(e.getPerson().withFirstName("John")))
.map(TODO) // add 1 year to experience duration .map(e -> e.withJobHistory(addOneYear(e.getJobHistory())))
.map(TODO) // replace qa with QA
* */
.map(e -> e.withPerson(e.getPerson().withFirstName("John")))
.map(e -> e.withJobHistory(addOneYear(e.getJobHistory())))
.map(e -> e.withJobHistory(replaceQA(e.getJobHistory())))
.getList();

final List<Employee> expectedResult =
Expand Down Expand Up @@ -108,26 +109,48 @@ public void mapping() {
assertEquals(mappedEmployees, expectedResult);
}

private List<JobHistoryEntry> replaceQA(List<JobHistoryEntry> jobHistory) {
return new MapHelper<>(jobHistory)
.map(j -> j.getPosition().equals("qa")
? j.withPosition("QA")
: j.withPosition(j.getPosition()))
.getList();
}

private List<JobHistoryEntry> addOneYear(List<JobHistoryEntry> jobHistory) {
return new MapHelper<>(jobHistory)
.map(j -> j.withDuration(j.getDuration() + 1))
.getList();
}


private static class LazyMapHelper<T, R> {
private List<T> list;
private Function<T, R> function;

public LazyMapHelper(List<T> list, Function<T, R> function) {
this.list = list;
this.function = function;
}

public static <T> LazyMapHelper<T, T> from(List<T> list) {
return new LazyMapHelper<>(list, Function.identity());
}

public List<R> force() {
// TODO
throw new UnsupportedOperationException();
List<R> result = new ArrayList<>();
for (T element : list) {
result.add(function.apply(element));
}

return result;
}

public <R2> LazyMapHelper<T, R2> map(Function<R, R2> f) {
// TODO
throw new UnsupportedOperationException();
}

return new LazyMapHelper<>(list, (function.andThen(f)));

}
}

private static class LazyFlatMapHelper<T, R> {
Expand Down Expand Up @@ -165,8 +188,6 @@ public <R2> LazyFlatMapHelper<T, R2> flatMap(Function<R, List<R2>> f) {
}
}



@Test
public void lazy_mapping() {
final List<Employee> employees =
Expand All @@ -193,6 +214,9 @@ public void lazy_mapping() {

final List<Employee> mappedEmployees =
LazyMapHelper.from(employees)
.map(e -> e.withPerson(e.getPerson().withFirstName("John")))
.map(e->e.withJobHistory(addOneYear(e.getJobHistory())))
.map(e ->e.withJobHistory(replaceQA(e.getJobHistory())))
/*
.map(TODO) // change name to John
.map(TODO) // add 1 year to experience duration
Expand Down