- implemented predefined interfaces task

 - added stream collect() examples

Author: Taras

lambda-basics/src/main/java/com/bobocode/LambdaTask_PredefinedInterfaces.java

@@ -3,6 +3,7 @@
 import com.bobocode.model.Account;
 
 import java.util.function.Predicate;
+import java.util.stream.IntStream;
 
 /**
  * Here you can find a list of various predefined interface variables. Your job is to provide implementation foe each
@@ -14,10 +15,16 @@ public static void main(String[] args) {
         // Predicates. As you remember Predicate<T> is a functional interface, its method test() receives one argument
         // with type T and returns boolean
 
-        Predicate<Integer> isNegative; // check whether a value is less than zero
-        Predicate<Account> useGoogle; // check whether its email ends with gmail.com
-        Predicate<Integer> isPrime; // implement logic that checks whether a number is prime
+        // check whether a value is less than zero
+        Predicate<Integer> isNegative = n -> n < 0;
+        // check whether its email ends with gmail.com
+        Predicate<Account> useGoogle = a -> a.getEmail().endsWith("gmail.com");
 
+        // implement logic that checks whether a number is prime
+        Predicate<Integer> isPrime = n -> IntStream.range(2, n).noneMatch(i -> n % i == 0);
+
+        IntStream.range(1, 50)
+                .forEach(i -> System.out.printf("%3d %10s\n", i, (isPrime.test(i) ? " is prime":"")));
 
     }
 

optional-basics/src/main/java/com/bobocode/util/TestDataProvider.java

@@ -19,7 +19,7 @@ public class StreamExamples_AdditionalFeatures {
     public static void main(String[] args) {
         List<Account> accounts = TestDataProvider.generateAccountList();
 
-        // Soring elements
+        // Sorting elements
         System.out.println("Account owner's sorter names: ");
         accounts.stream()
                 .sorted(comparing(Account::getFirstName))

stream-api/src/main/java/com/bobocode/StreamExamples_AdditionalFeatures.java

@@ -5,9 +5,12 @@
 import com.bobocode.util.TestDataProvider;
 
 import java.time.Month;
+import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 
+import static java.util.Comparator.*;
 import static java.util.stream.Collectors.*;
 
 /**
@@ -56,5 +59,24 @@ public static void main(String[] args) {
                 .map(Account::getFirstName)
                 .collect(joining(", "));
         System.out.println(concatenatedName);
+
+
+        Map<Boolean, List<Account>> accountByNameLength = accounts.stream()
+                .collect(partitioningBy(a -> a.getFirstName().length() > 4));
+
+        Map<Boolean, Optional<Account>> lengthNameAccountsWithMaxBalance = accounts.stream()
+                .collect(
+                        partitioningBy(a -> a.getFirstName().length() > 4,
+                                maxBy(comparing(Account::getBalance)))
+                );
+
+
+        Map<Boolean, Map<Month, List<String>>> accountByNameLengthByBirthdayMonth = accounts.stream()
+                .collect(partitioningBy(a -> a.getFirstName().length() > 4,
+                        groupingBy(a -> a.getBirthday().getMonth(),
+                                mapping(Account::getFirstName, toList()))));
+
+        System.out.println(accountByNameLengthByBirthdayMonth);
+
     }
 }