Solutions

Daniel Reuter · Daniel Reuter · commit 34cc0db8abec · 2013-11-29T15:29:38.000+01:00
diff --git a/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java b/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
@@ -1,13 +1,16 @@
 package de.codecentric.java8examples.streaming;
 
+import java.time.LocalDate;
+import java.time.Period;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
 import de.codecentric.java8examples.Invoice;
 import de.codecentric.java8examples.InvoiceItem;
 import de.codecentric.java8examples.Person;
 
-import java.util.Collections;
-import java.util.List;
-import java.util.Set;
-
 /**
  * Your task: Implement the following methods and make the tests passs.
  */
@@ -17,44 +20,58 @@ public class FilteringAndMapping {
      * Extract a list of names (firstname and lastname separated by space) from a given list of Person objects.
      */
     public static List<String> extractNames(List<Person> persons) {
-        return Collections.emptyList();
+	return persons.stream()//
+		.<String> map(p -> p.getFirstName() + " " + p.getLastName())//
+		.collect(Collectors.<String> toList());
     }
 
     /**
-     * Extract a sorted (ascending by lastname) list of names (firstname and lastname separated by space) from a
-     * given list of Person objects.
+     * Extract a sorted (ascending by lastname) list of names (firstname and lastname separated by space) from a given list of Person objects.
      */
     public static List<String> extractNamesSortedByLastname(List<Person> persons) {
-        return Collections.emptyList();
+	return persons.stream()//
+		.sorted((Person p1, Person p2) -> (p1.getLastName().compareTo(p2.getLastName())))//
+		.<String> map(p -> p.getFirstName() + " " + p.getLastName())//
+		.collect(Collectors.<String> toList());
     }
 
     /**
      * From a given list of Person objects, extract a list of female firstnames
      */
     public static List<String> extractFemaleFirstnames(List<Person> persons) {
-        return Collections.emptyList();
+	return persons.stream()//
+		.filter(p -> p.getGender().equals(Person.Gender.FEMALE))//
+		.<String> map(p -> p.getFirstName())//
+		.collect(Collectors.<String> toList());
     }
 
     /**
      * Extract all females older than 18 years from a given list of Person objects.
      */
     public static List<Person> extractAdultWomen(List<Person> persons) {
-        return Collections.emptyList();
+	return persons.stream()//
+		.filter(p -> p.getGender().equals(Person.Gender.FEMALE))//
+		.filter((Person p) -> Period.between(p.getBirthDay(), LocalDate.now()).getYears() >= 18)//
+		.collect(Collectors.<Person> toList());
     }
 
     /**
-     * From a given list of Person objects, extract a set of firstnames of the people whose lastname starts
-     * with the given string.
+     * From a given list of Person objects, extract a set of firstnames of the people whose lastname starts with the given string.
      */
     public static Set<String> extractFirstnamesWhereLastnameStartsWith(List<Person> persons, String startsWith) {
-        return Collections.emptySet();
+	return persons.stream()//
+		.filter((Person p) -> p.getLastName().startsWith(startsWith))//
+		.<String> map(p -> p.getFirstName())//
+		.collect(Collectors.<String> toSet());
     }
 
     /**
      * From a given list of invoices, extract a set of all product names.
      */
     public static Set<String> extractAllProducts(List<Invoice> invoices) {
-        return Collections.emptySet();
+	return invoices.stream()//
+		.<InvoiceItem> flatMap((Invoice i) -> i.getItems().stream())//
+		.<String> map((InvoiceItem i) -> i.getProduct())//
+		.collect(Collectors.<String> toSet());
     }
 }
-
