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Part 3 (partially) #181

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57 changes: 38 additions & 19 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> newList = new ArrayList<>();
list.forEach(
(T t) -> newList.add(f.apply(t))
);
return new MapHelper<R>(newList);
}

// [T] -> (T -> [R]) -> [R]
Expand All @@ -50,6 +53,19 @@ public <R> MapHelper<R> flatMap(Function<T, List<R>> f) {
}
}


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

private static List<JobHistoryEntry> replace(List<JobHistoryEntry> jobHistoryEntries){
return new MapHelper<JobHistoryEntry>(jobHistoryEntries)
.map(e -> e.withPosition(e.getPosition().replace("qa","QA")))
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@senia-psm senia-psm Jul 17, 2017

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Don't replace qabalah specialist with QAbalah specialist

.getList();
}

@Test
public void mapping() {
final List<Employee> employees =
Expand All @@ -76,12 +92,10 @@ 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
* */
.getList();
.map(e -> e.withPerson(e.getPerson().withFirstName("John")))
.map(e -> e.withJobHistory(addOneYear(e.getJobHistory())))
.map(e -> e.withJobHistory(replace(e.getJobHistory())))
.getList();

final List<Employee> expectedResult =
Arrays.asList(
Expand Down Expand Up @@ -111,21 +125,28 @@ public void mapping() {

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<R>();
list.forEach(e -> result.add(function.apply(e)));
return result;
}


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

}
Expand Down Expand Up @@ -166,7 +187,6 @@ public <R2> LazyFlatMapHelper<T, R2> flatMap(Function<R, List<R2>> f) {
}



@Test
public void lazy_mapping() {
final List<Employee> employees =
Expand All @@ -191,14 +211,13 @@ public void lazy_mapping() {
))
);


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

final List<Employee> expectedResult =
Arrays.asList(
Expand Down