From 9b514c8414edffa7f1cba6584b07f3908fdf4f86 Mon Sep 17 00:00:00 2001
From: "Dr. Martin Goik" <goik@hdm-stuttgart.de>
Date: Sun, 14 Oct 2018 12:31:52 +0200
Subject: [PATCH] Better separation of test code + explanations
---
.../mi/javastreams/Java8FunctionalTest.java | 306 ++++++++++--------
1 file changed, 163 insertions(+), 143 deletions(-)
diff --git a/P/Sda1/Streams/Solution/src/test/java/de/hdm_stuttgart/mi/javastreams/Java8FunctionalTest.java b/P/Sda1/Streams/Solution/src/test/java/de/hdm_stuttgart/mi/javastreams/Java8FunctionalTest.java
index 57cee719c..3b9d0a1d1 100644
--- a/P/Sda1/Streams/Solution/src/test/java/de/hdm_stuttgart/mi/javastreams/Java8FunctionalTest.java
+++ b/P/Sda1/Streams/Solution/src/test/java/de/hdm_stuttgart/mi/javastreams/Java8FunctionalTest.java
@@ -6,6 +6,7 @@ import java.util.*;
import java.util.stream.Collector;
import java.util.stream.Collectors;
+import com.github.npathai.hamcrestopt.OptionalMatchers;
import org.hamcrest.Matchers;
import org.junit.Assert;
import org.junit.FixMethodOrder;
@@ -25,10 +26,10 @@ public class Java8FunctionalTest {
static private final List<Student> students = ImmutableList.of(
new Student("Fred", 2, Student.Sex.MALE, "fred@example.com")
- ,new Student("Jane", 1, Student.Sex.FEMALE, "jane@kiv.de")
- ,new Student("George", 4, Student.Sex.MALE, "george@math.edu")
- ,new Student("Bob", 2, Student.Sex.MALE, "bob@uk.edu")
- ,new Student("Kim", 2, Student.Sex.FEMALE, "wilde@serious.de")
+ ,new Student("Jane", 1, Student.Sex.FEMALE, "jane@kiv.de")
+ ,new Student("George",4, Student.Sex.MALE, "george@math.edu")
+ ,new Student("Bob", 2, Student.Sex.MALE, "bob@uk.edu")
+ ,new Student("Kim", 2, Student.Sex.FEMALE, "wilde@serious.de")
);
/**
@@ -36,11 +37,11 @@ public class Java8FunctionalTest {
* names alphabetically ordered eliminating possible duplicates. Implementation hints:</p>
*
* <pre
- * >"Fred", 2, Student.Sex.MALE, "fred@example.com"
- * "Jane", 1, Student.Sex.FEMALE, "jane@kiv.de"
- * "George", 4, Student.Sex.MALE, "george@math.edu"
- * "Bob", 2, Student.Sex.MALE, "bob@uk.edu"
- * "Kim", 2, Student.Sex.FEMALE, "wilde@serious.de"</pre>
+ * >{"Fred", 2, Student.Sex.MALE, "fred@example.com"}
+ * {"Jane", 1, Student.Sex.FEMALE, "jane@kiv.de"}
+ * {"George", 4, Student.Sex.MALE, "george@math.edu"}
+ * {"Bob", 2, Student.Sex.MALE, "bob@uk.edu"}
+ * {"Kim", 2, Student.Sex.FEMALE, "wilde@serious.de"}</pre>
*
* <p>Result: {"Bob", "Fred", "George"}</p>
*/
@@ -48,19 +49,19 @@ public class Java8FunctionalTest {
public void allMaleDistinctNameOrderedByEmail() {
final List<String> emails =
- students.parallelStream().
- filter(s -> s.gender == Sex.MALE).
- sorted(Comparator.comparing(Student::getEmailAddress)).
- map(Student::getName).
- distinct().
- collect(Collectors.toList());
+ students.parallelStream().
+ filter(s -> s.gender == Sex.MALE).
+ sorted(Comparator.comparing(Student::getEmailAddress)).
+ map(Student::getName).
+ distinct().
+ collect(Collectors.toList());
assertThat(
- emails,
- Matchers.equalTo(
- ImmutableList.of("Bob", "Fred", "George")
- )
- );
+ emails,
+ Matchers.equalTo(
+ ImmutableList.of("Bob", "Fred", "George")
+ )
+ );
}
/**
@@ -80,84 +81,96 @@ public class Java8FunctionalTest {
* <dd>Expected value: 1 + 2 == 3</dd>
* </dl>
*
- * <p>Implementation hint: Process a stream of Student instances by:</p>
+ * <p>Implementation hint: Process a stream of {@link Student} instances by:</p>
*
* <ol>
* <li>Filter students having a german email.</li>
- * <li>Map objects to int.</li>
+ * <li>Map objects to mark values of type int.</li>
* <li>Provide a suitable
* <a href="https://docs.oracle.com/javase/tutorial/collections/streams/reduction.html#reduce"
- * >reduce operation</a>. You may safely assume the existence of at least one Student.</li>
+ * >reduce operation</a>. You may safely assume the existence of at least one student.</li>
* </ol>
*
- * <p>You may want to read
+ * <p>You may also want to read
* <a href="https://docs.oracle.com/javase/tutorial/collections/streams/reduction.html#reduce"
* >https://docs.oracle.com/javase/tutorial/collections/streams/reduction.html#reduce</a>.</p>
*/
@Test
public void markSumAllStudentsMarksHavingEmail_Dot_de() {
- Assert.assertEquals(
- 3, //Expected marks sum 3 == 1 + 2
- students.parallelStream()
- .filter(p -> p.emailAddress.endsWith(".de")) // Jane and Kim
- .mapToInt(Student::getMark)
- .reduce(0, (a, b) -> a + b)
- );
+
+ final int sumMarksOfStudentsHavingGermanEmail = students.parallelStream()
+ .filter(p -> p.emailAddress.endsWith(".de")) // Jane and Kim
+ .mapToInt(Student::getMark)
+ .reduce(0, (a, b) -> a + b);
+
+ assertThat(sumMarksOfStudentsHavingGermanEmail, Matchers.equalTo(3));
}
/**
- * <p>A comma separated string containing all students' alphabetically ordered
- * email addresses:</p>
+ * <p>A comma separated string containing all students' alphabetically ordered email addresses:</p>
*
- * "bob@uk.edu, fred@example.com, george@math.edu, ..."
- *
+ * <p>{"bob@uk.edu, fred@example.com, george@math.edu, ..."}</p>
+ *
+ * <p>Implementation hint: Process a stream of {@link Student} instances by:</p>
+ *
+ * <ol>
+ * <li>Map {@link Student} instances to their emails.</li>
+ * <li>Sort alphabetically.</li>
+ * <li>Use <a href="https://www.baeldung.com/java-8-collectors">a suitable</a> {@link Collector}.</li>
+ * </ol>
*/
@Test
public void orderedCharacterSeparatedEmailList() {
- Assert.assertEquals(
- "bob@uk.edu, fred@example.com, george@math.edu, jane@kiv.de, wilde@serious.de",
-
- students.parallelStream().
- map(Student::getEmailAddress).
- sorted().
- collect(new CsvCollector(", ")) // Using ", " as separator string.
- );
+ final String csvSortedEmails = students.stream().
+ map(Student::getEmailAddress).
+ sorted().
+ collect(Collectors.joining(", "));
+ assertThat(
+ csvSortedEmails,
+ Matchers.equalTo("bob@uk.edu, fred@example.com, george@math.edu, jane@kiv.de, wilde@serious.de")
+ );
}
/**
* Achieves the same result as in {@link #orderedCharacterSeparatedEmailList()}
- * internally using a standard collector with a modified
- * {@link Collector#finisher()} method:
- *
- * "bob@uk.edu, fred@example.com, george@math.edu, ..."
- *
+ * internally using <a href="https://www.baeldung.com/java-8-streams#reduction">reduction</a>:
+ *
+ * <p>Implementation hint: Process a stream of {@link Student} instances by:</p>
+ *
+ * <ol>
+ * <li>Map {@link Student} instances to their emails.</li>
+ * <li>Sort alphabetically.</li>
+ * <li>Implement a suitable reducing operation turning a stream of email adresses into
+ * a single String containing comma separated email adresses.</li>
+ * <li>You may safely assume at least one email to be present.</li>
+ * </ol>
*/
@Test
public void orderedCharacterSeparatedEmailList2() {
- Assert.assertEquals(
- "bob@uk.edu, fred@example.com, george@math.edu, jane@kiv.de, wilde@serious.de",
+ final Optional<String> emailCsvList =
+ students.parallelStream().
+ map(Student::getEmailAddress).
+ sorted().
+ reduce((s, t) -> s + ", " + t);
- students.parallelStream().
- map(Student::getEmailAddress).
- sorted().
- collect
- (Collectors.collectingAndThen
- (Collectors.toList(),
- l -> l.stream(). // A stream within a stream.
- reduce((s1, s2) -> s1 + ", " + s2).
- get()
- )
- )
- );
+ assertThat(emailCsvList, OptionalMatchers.isPresentAndIs(
+ "bob@uk.edu, fred@example.com, george@math.edu, jane@kiv.de, wilde@serious.de"));
}
/**
- * Get the average mark of all female students as double value.
- *
- * Female marks: {1, 2}, sum == 3, average = 3. / 2 == 1.5
+ * <p>Get the average mark of all female students as double value.</p>
+ *
+ * <pre
+ * >{"Jane", 1, Student.Sex.FEMALE, "jane@kiv.de"}
+ * {"Kim", 2, Student.Sex.FEMALE, "wilde@serious.de"}</pre>
+ *
+ *
+ * <p>Female student marks sum: 1 + 2 == 3</p>
+ *
+ * <p>Result: average = 3. / 2 == 1.5</p>
*
*/
@Test
@@ -169,48 +182,45 @@ public class Java8FunctionalTest {
mapToInt(Student::getMark).
average();
+ // No suitable matcher on offer
Assert.assertTrue(femaleAverage.isPresent());
Assert.assertEquals((1 + 2) / 2., femaleAverage.getAsDouble(), 1.E-20);
}
/**
- * Group students by sex and collect their respective names:
+ * Create a {@code Map<Student.Sex, List<String>>} grouping students by sex and collecting their respective names:
*
- * Female:
- * "Jane"
- * "Kim"
- *
- * Male:
- * "Fred"
- * "George"
- * "Bob"
+ * {
+ * Female: {"Jane", "Kim"},
+ * Male: {"Fred", "George", "Bob"}
+ * }
*
*/
@Test
public void studentNamesBySex() {
final Map<Student.Sex, List<String>> studentnamesBySex =
- students
- .parallelStream()
+ students.parallelStream()
.collect(
- Collectors.groupingBy(
- Student::getSex,
- Collectors.mapping(
- Student::getName,
- Collectors.toList())
- )
- );
+ Collectors.groupingBy(
+ Student::getSex,
+ Collectors.mapping(
+ Student::getName,
+ Collectors.toList()
+ )
+ )
+ );
assertThat(
- studentnamesBySex,
- Matchers.<Map<Student.Sex, List<String>>> equalTo(
- ImmutableMap.of (
- Student.Sex.MALE, ImmutableList.of("Fred", "George", "Bob"),
- Student.Sex.FEMALE, ImmutableList.of("Jane", "Kim")
- )
- )
- );
+ studentnamesBySex,
+ Matchers.equalTo(
+ ImmutableMap.of (
+ Student.Sex.MALE, ImmutableList.of("Fred", "George", "Bob"),
+ Student.Sex.FEMALE, ImmutableList.of("Jane", "Kim")
+ )
+ )
+ );
}
/**
@@ -219,73 +229,83 @@ public class Java8FunctionalTest {
* Mark 1: "Jane" --- 1 student
* Mark 2: "Fred", "Bob", "Kim" --- 3 students
* Mark 4: "George" --- 1 student
+ *
+ * Result:
+ *
+ * <pre>{
+ * 1: 1,
+ * 2: 3,
+ * 4: 1
+ * }</pre>
*
*/
@Test
public void markingFrequencies() {
final Map<Integer, Integer> frequencyByMark =
- students
- .parallelStream()
- .collect(
- Collectors.groupingBy(
- Student::getMark,
- Collectors.reducing(
- 0,
- s -> 1,// counting heads.
- Integer::sum)
- )
- );
+ students
+ .parallelStream()
+ .collect(
+ Collectors.groupingBy(
+ Student::getMark,
+ Collectors.reducing(
+ 0,
+ s -> 1, // counting heads.
+ Integer::sum
+ )
+ )
+ );
- assertThat(frequencyByMark,
- Matchers.equalTo(
- ImmutableMap.of(
- 1, 1,
- 2, 3,
- 4, 1
- )
- )
- );
+ assertThat(
+ frequencyByMark,
+ Matchers.equalTo(
+ ImmutableMap.of(
+ 1, 1,
+ 2, 3,
+ 4, 1
+ )
+ )
+ );
}
/**
- * Students' names in ascending order grouped by by marking category:
- *
- * Mark 1: {"Jane"}
- * Mark 2: {"Bob", "Fred", "Kim"}
- * Mark 4: {"George"}
+ * Students' names as {@code List<String>} in ascending order grouped by by mark values:
+ * <pre>{
+ * 1: {"Jane"}
+ * 2: {"Bob", "Fred", "Kim"}
+ * 4: {"George"}
+ * }</pre>
*
*/
@Test
- public void studentnamessByMark() {
+ public void studentnamesByMark() {
final Map<Integer, List<String>> namesByMark =
- students
- .parallelStream()
- .collect(
+ students.parallelStream().
+ collect(
Collectors.groupingBy(
- Student::getMark,
- Collectors.mapping(
- Student::getName,
- Collectors.collectingAndThen(
- Collectors.toList(),
- l -> {
- Collections.sort(l);
- return l;
- }
- )
- )
- )
- );
+ Student::getMark,
+ Collectors.mapping(
+ Student::getName,
+ Collectors.collectingAndThen(
+ Collectors.toList(),
+ l -> {
+ Collections.sort(l);
+ return l;
+ }
+ )
+ )
+ )
+ );
assertThat(
- namesByMark,
- Matchers.<Map<Integer, List<String>>> equalTo (
- ImmutableMap.of(
- 1, ImmutableList.of("Jane"),
- 2, ImmutableList.of("Bob", "Fred", "Kim"),
- 4, ImmutableList.of("George")
- )
- )
- );
+ namesByMark,
+ Matchers.equalTo (
+ ImmutableMap.of(
+ 1, ImmutableList.of("Jane"),
+ 2, ImmutableList.of("Bob", "Fred", "Kim"),
+ 4, ImmutableList.of("George")
+ )
+ )
+ );
}
-}
+}
\ No newline at end of file
--
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