Complete AccountAnalytics.java exercise

Author: tboychuk

account-analytics/src/main/java/com.bobocode/AccountAnalytics.java

@@ -6,7 +6,10 @@
 import java.math.BigDecimal;
 import java.time.Month;
 import java.util.*;
+import java.util.function.Function;
+import java.util.stream.Stream;
 
+import static java.util.Comparator.comparing;
 import static java.util.stream.Collectors.*;
 
 /**
@@ -30,7 +33,7 @@ private AccountAnalytics(Collection<Account> accounts) {
      */
     public Optional<Account> findRichestPerson() {
         return accounts.stream()
-                .max(Comparator.comparing(Account::getBalance));
+                .max(comparing(Account::getBalance));
     }
 
     /**
@@ -53,7 +56,7 @@ public List<Account> findAccountsByBirthdayMonth(Month birthdayMonth) {
      */
     public Map<Boolean, List<Account>> partitionMaleAccounts() {
         return accounts.stream()
-                .collect(partitioningBy(a->a.getSex().equals(Sex.MALE)));
+                .collect(partitioningBy(a -> a.getSex().equals(Sex.MALE)));
     }
 
     /**
@@ -73,7 +76,9 @@ public Map<String, List<Account>> groupAccountsByEmailDomain() {
      * @return total number of letters of first names of all accounts
      */
     public int getNumOfLettersInFirstAndLastNames() {
-        throw new UnsupportedOperationException("It's your job to implement this method"); // todo
+        return accounts.stream()
+                .mapToInt(a -> a.getFirstName().length() + a.getLastName().length())
+                .sum();
     }
 
     /**
@@ -82,7 +87,9 @@ public int getNumOfLettersInFirstAndLastNames() {
      * @return total balance of all accounts
      */
     public BigDecimal calculateTotalBalance() {
-        throw new UnsupportedOperationException("It's your job to implement this method"); // todo
+        return accounts.stream()
+                .map(Account::getBalance)
+                .reduce(BigDecimal.ZERO, BigDecimal::add);
     }
 
     /**
@@ -91,7 +98,10 @@ public BigDecimal calculateTotalBalance() {
      * @return list of accounts sorted by first and last names
      */
     public List<Account> sortByFirstAndLastNames() {
-        throw new UnsupportedOperationException("It's your job to implement this method"); // todo
+        return accounts.stream()
+                .sorted(comparing(Account::getFirstName)
+                        .thenComparing(Account::getLastName))
+                .collect(toList());
     }
 
     /**
@@ -101,7 +111,8 @@ public List<Account> sortByFirstAndLastNames() {
      * @return a map where key is a first name and value is a set of first names
      */
     public Map<String, Set<String>> groupFirstNamesByLastNames() {
-        throw new UnsupportedOperationException("It's your job to implement this method"); // todo
+        return accounts.stream()
+                .collect(groupingBy(Account::getLastName, mapping(Account::getFirstName, toSet())));
     }
 
     /**
@@ -111,7 +122,9 @@ public Map<String, Set<String>> groupFirstNamesByLastNames() {
      * @return a map where a key is a birthday month and value is comma-separated first names
      */
     public Map<Month, String> groupCommaSeparatedFirstNamesByBirthdayMonth() {
-        throw new UnsupportedOperationException("It's your job to implement this method"); // todo
+        return accounts.stream()
+                .collect(groupingBy(a -> a.getBirthday().getMonth(),
+                        mapping(Account::getFirstName, joining(", "))));
     }
 
     /**
@@ -121,7 +134,10 @@ public Map<Month, String> groupCommaSeparatedFirstNamesByBirthdayMonth() {
      * @return a map where key is a creation month and value is total balance of all accounts created in that month
      */
     public Map<Month, BigDecimal> groupTotalBalanceByCreationMonth() {
-        throw new UnsupportedOperationException("It's your job to implement this method"); // todo
+        return accounts.stream()
+                .collect(groupingBy(a -> a.getCreationDate().getMonth(),
+                        mapping(Account::getBalance,
+                                reducing(BigDecimal.ZERO, BigDecimal::add))));
     }
 
     /**
@@ -131,7 +147,11 @@ public Map<Month, BigDecimal> groupTotalBalanceByCreationMonth() {
      * @return a map where key is a letter and value is its count in all first names
      */
     public Map<Character, Long> getCharacterFrequencyInFirstNames() {
-        throw new UnsupportedOperationException("It's your job to implement this method"); // todo
+        return accounts.stream()
+                .map(Account::getFirstName)
+                .flatMapToInt(String::chars)
+                .mapToObj(c -> (char) c)
+                .collect(groupingBy(Function.identity(), counting()));
     }
 
     /**
@@ -141,7 +161,12 @@ public Map<Character, Long> getCharacterFrequencyInFirstNames() {
      * @return a map where key is a letter and value is its count ignoring case in all first and last names
      */
     public Map<Character, Long> getCharacterFrequencyIgnoreCaseInFirstAndLastNames() {
-        throw new UnsupportedOperationException("It's your job to implement this method"); // todo
+        return accounts.stream()
+                .flatMap(a -> Stream.of(a.getFirstName(), a.getLastName()))
+                .map(String::toLowerCase)
+                .flatMapToInt(String::chars)
+                .mapToObj(c -> (char) c)
+                .collect(groupingBy(Function.identity(), counting()));
     }