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Drozdov Igor part3 #174

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68 changes: 44 additions & 24 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 @@ -9,7 +9,6 @@
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
Expand All @@ -32,8 +31,10 @@ 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<R>();
list.forEach((T t) -> result.add(f.apply(t)));

return new MapHelper<R>(result);
}

// [T] -> (T -> [R]) -> [R]
Expand Down Expand Up @@ -76,11 +77,9 @@ 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(employee -> employee.withPerson(employee.getPerson().withFirstName("John")))
.map(employee -> employee.withJobHistory(addOneYear(employee.getJobHistory())))
.map(employee -> employee.withJobHistory(replaceQA(employee.getJobHistory())))
.getList();

final List<Employee> expectedResult =
Expand Down Expand Up @@ -108,47 +107,68 @@ public void mapping() {
assertEquals(mappedEmployees, expectedResult);
}

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

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

private static class LazyMapHelper<T, R> {
private final List<T> list;
private final 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();
return new MapHelper<>(list).map(function).getList();
}

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

}

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

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

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

public List<R> force() {
// TODO
throw new UnsupportedOperationException();
return new MapHelper<>(list).map(function).getList();
}

public LazyFlatMapHelper<T, R> filter(Predicate<R> p) {
return flatMap(r -> p.test(r) ? Collections.singletonList(r) : Collections.emptyList());
}

// TODO filter
// (T -> boolean) -> (T -> [T])
// filter: [T1, T2] -> (T -> boolean) -> [T2]
// flatMap": [T1, T2] -> (T -> [T]) -> [T2]

public <R2> LazyFlatMapHelper<T, R2> map(Function<R, R2> f) {
final Function<R, List<R2>> listFunction = rR2TorListR2(f);
return flatMap(listFunction);
Expand All @@ -165,7 +185,9 @@ public <R2> LazyFlatMapHelper<T, R2> flatMap(Function<R, List<R2>> f) {
}
}


interface Traversable<T> {
void forEach(Consumer<T> consumer);
}

@Test
public void lazy_mapping() {
Expand Down Expand Up @@ -193,11 +215,9 @@ 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
* */
.map(employee -> employee.withPerson(employee.getPerson().withFirstName("John")))
.map(employee -> employee.withJobHistory(addOneYear(employee.getJobHistory())))
.map(employee -> employee.withJobHistory(replaceQA(employee.getJobHistory())))
.force();

final List<Employee> expectedResult =
Expand Down