Created first version of the program.

src/main/java/practice/CandidateValidator.java

@@ -1,5 +1,27 @@
 package practice;
 
-public class CandidateValidator {
-    //write your code here
+import java.util.function.Predicate;
+import model.Candidate;
+
+public class CandidateValidator implements Predicate<Candidate> {
+    private static final int MIN_YEARS_OLD = 35;
+    private static final int MIN_TOTAL_DURATION = 10;
+    private static final String VALID_NATIONALITY = "Ukrainian";
+    private static final String REGEX = "-";
+    private static final int SINCE_YEAR_INDEX = 0;
+    private static final int TO_YEAR_INDEX = 1;
+
+    @Override
+    public boolean test(Candidate candidate) {
+        if (candidate.getAge() >= MIN_YEARS_OLD && candidate.isAllowedToVote()
+                && VALID_NATIONALITY.equals(candidate.getNationality())) {
+            String[] years = candidate.getPeriodsInUkr().split(REGEX);
+
+            int totalDuration = Integer.parseInt(years[TO_YEAR_INDEX])
+                    - Integer.parseInt(years[SINCE_YEAR_INDEX]);
+
+            return totalDuration >= MIN_TOTAL_DURATION;
+        }
+        return false;
+    }
 }

src/main/java/practice/StreamPractice.java

@@ -1,11 +1,17 @@
 package practice;
 
-import java.util.Collections;
+import java.util.Collection;
 import java.util.List;
+import java.util.function.Predicate;
+import java.util.stream.IntStream;
 import model.Candidate;
+import model.Cat;
 import model.Person;
 
 public class StreamPractice {
+    private static final String EXCEPTION_MESSAGE = "Can't get min value from list: ";
+    private static final String REGEX = ",";
+
     /**
      * Given list of strings where each element contains 1+ numbers:
      * input = {"5,30,100", "0,22,7", ...}
@@ -14,7 +20,13 @@ public class StreamPractice {
      * "Can't get min value from list: < Here is our input 'numbers' >"
      */
     public int findMinEvenNumber(List<String> numbers) {
-        return 0;
+        return numbers.stream()
+                .map(string -> List.of(string.split(REGEX)))
+                .flatMap(Collection::stream)
+                .mapToInt(Integer::parseInt)
+                .filter(number -> !isOddNumber(number))
+                .min()
+                .orElseThrow(() -> new RuntimeException(EXCEPTION_MESSAGE + numbers));
     }
 
     /**
@@ -23,7 +35,15 @@ public int findMinEvenNumber(List<String> numbers) {
      * But before that subtract 1 from each element on an odd position (having the odd index).
      */
     public Double getOddNumsAverage(List<Integer> numbers) {
-        return 0D;
+        return IntStream.range(0, numbers.size())
+                .map(index -> isOddNumber(index) ? numbers.get(index) - 1 : numbers.get(index))
+                .filter(StreamPractice::isOddNumber)
+                .average()
+                .getAsDouble();
+    }
+
+    private static boolean isOddNumber(int number) {
+        return number % 2 != 0;
     }
 
     /**
@@ -35,7 +55,10 @@ public Double getOddNumsAverage(List<Integer> numbers) {
      * Example: select men who can be recruited to army (from 18 to 27 years old inclusively).
      */
     public List<Person> selectMenByAge(List<Person> peopleList, int fromAge, int toAge) {
-        return Collections.emptyList();
+        return peopleList.stream()
+                .filter(person -> fromAge <= person.getAge() && person.getAge() <= toAge
+                        && person.getSex() == Person.Sex.MAN)
+                .toList();
     }
 
     /**
@@ -50,7 +73,17 @@ public List<Person> selectMenByAge(List<Person> peopleList, int fromAge, int toA
      */
     public List<Person> getWorkablePeople(int fromAge, int femaleToAge,
                                           int maleToAge, List<Person> peopleList) {
-        return Collections.emptyList();
+        Predicate<Person> isAgeInRange = person -> {
+            int age = person.getAge();
+            Person.Sex sex = person.getSex();
+
+            return (sex == Person.Sex.MAN && age >= fromAge && age <= maleToAge)
+                    || (sex == Person.Sex.WOMAN && age >= fromAge && age <= femaleToAge);
+        };
+
+        return peopleList.stream()
+                .filter(isAgeInRange)
+                .toList();
     }
 
     /**
@@ -59,7 +92,12 @@ public List<Person> getWorkablePeople(int fromAge, int femaleToAge,
      * return the names of all cats whose owners are women from `femaleAge` years old inclusively.
      */
     public List<String> getCatsNames(List<Person> peopleList, int femaleAge) {
-        return Collections.emptyList();
+        return peopleList.stream()
+                .filter(p -> p.getSex() == Person.Sex.WOMAN && p.getAge() >= femaleAge)
+                .map(Person::getCats)
+                .flatMap(Collection::stream)
+                .map(Cat::getName)
+                .toList();
     }
 
     /**
@@ -75,6 +113,11 @@ public List<String> getCatsNames(List<Person> peopleList, int femaleAge) {
      * parametrized with Candidate in CandidateValidator.
      */
     public List<String> validateCandidates(List<Candidate> candidates) {
-        return Collections.emptyList();
+        CandidateValidator candidateValidator = new CandidateValidator();
+        return candidates.stream()
+                .filter(candidateValidator)
+                .map(Candidate::getName)
+                .sorted()
+                .toList();
     }
 }