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Part 3 (by Vasilii Bobkov) #183

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Part 3 (by Vasilii Bobkov) #183

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60 changes: 37 additions & 23 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 @@ -9,10 +9,7 @@
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;

import static org.junit.Assert.assertEquals;

Expand All @@ -32,8 +29,11 @@ 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<>();
for (T element : list) {
newList.add(f.apply(element));
}
return new MapHelper<>(newList);
}

// [T] -> (T -> [R]) -> [R]
Expand Down Expand Up @@ -76,12 +76,10 @@ 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(replaceQaToUpperCase(e.getJobHistory()))) // replace qa with QA
.getList();

final List<Employee> expectedResult =
Arrays.asList(
Expand All @@ -108,24 +106,44 @@ public void mapping() {
assertEquals(mappedEmployees, expectedResult);
}

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

private List<JobHistoryEntry> replaceQaToUpperCase(List<JobHistoryEntry> jobHistoryEntries) {
MapHelper<JobHistoryEntry> mapHelper = new MapHelper<>(jobHistoryEntries);
return mapHelper
.map(entry -> entry.getPosition().equals("qa") ? entry.withPosition("QA") : entry)
.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();
final 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();
Function<T, R2> newFunction = function.andThen(f);
return new LazyMapHelper<>(list, newFunction);
}

}
Expand Down Expand Up @@ -165,8 +183,6 @@ public <R2> LazyFlatMapHelper<T, R2> flatMap(Function<R, List<R2>> f) {
}
}



@Test
public void lazy_mapping() {
final List<Employee> employees =
Expand All @@ -193,12 +209,10 @@ 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(replaceQaToUpperCase(e.getJobHistory())))
.force();

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