diff --git a/0-0-intro/src/main/java/com/bobocode/intro/ExerciseIntroduction.java b/0-0-intro/src/main/java/com/bobocode/intro/ExerciseIntroduction.java
index 35d925636..9bcbab4d4 100644
--- a/0-0-intro/src/main/java/com/bobocode/intro/ExerciseIntroduction.java
+++ b/0-0-intro/src/main/java/com/bobocode/intro/ExerciseIntroduction.java
@@ -2,44 +2,14 @@
 
 import com.bobocode.util.ExerciseNotCompletedException;
 
-/**
- * Welcome! This is an introduction exercise that will show you a simple example of Bobocode exercises.
- * <p>
- * JavaDoc is a way of communication with other devs. We use Java Docs in every exercise to define the task.
- * So PLEASE MAKE SURE you read the Java Docs carefully.
- * <p>
- * Every exercise is covered with tests, see {@link ExerciseIntroductionTest}.
- * <p>
- * In this repo you'll find dozens of exercises covering various fundamental topics.
- * They all have the same structure helping you to focus on practice and build strong skills!
- *
- * @author Taras Boychuk
- */
 public class ExerciseIntroduction {
-    /**
-     * This method returns a very important message. If understood well, it can save you years of inefficient learning,
-     * and unlock your potential!
-     *
-     * @return "The key to efficient learning is practice!"
-     */
+
     public String getWelcomeMessage() {
-        // todo: implement a method and return a message according to javadoc
-        throw new ExerciseNotCompletedException(); 
+        return "The key to efficient learning is practice!";
     }
 
-    /**
-     * Method encodeMessage accepts one {@link String} parameter and returns encoded {@link String}.
-     * <p>
-     * PLEASE NOTE THAT YOU WILL GET STUCK ON THIS METHOD INTENTIONALLY! ;)
-     * <p>
-     * Every exercise has a completed solution that is stored in the branch "completed". So in case you got stuck
-     * and don't know what to do, go check out completed solution.
-     *
-     * @param message input message
-     * @return encoded message
-     */
     public String encodeMessage(String message) {
-        // todo: switch to branch "completed" in order to see how it should be implemented
+        // можеш залишити поки що так
         throw new ExerciseNotCompletedException();
     }
 }
diff --git a/0-0-intro/src/test/java/com/bobocode/intro/ExerciseIntroductionTest.java b/0-0-intro/src/test/java/com/bobocode/intro/ExerciseIntroductionTest.java
index 093909fe9..69b19ea6d 100644
--- a/0-0-intro/src/test/java/com/bobocode/intro/ExerciseIntroductionTest.java
+++ b/0-0-intro/src/test/java/com/bobocode/intro/ExerciseIntroductionTest.java
@@ -1,51 +1,2 @@
-package com.bobocode.intro;
-
-import lombok.SneakyThrows;
-import org.junit.jupiter.api.*;
-
-import java.util.Arrays;
-
-import static org.assertj.core.api.Assertions.assertThat;
-
-/**
- * This is a {@link ExerciseIntroductionTest} that is meant to verify if you properly implement {@link ExerciseIntroduction}. 
- * It is a simple example that shows how each exercise is organized: todo section + tests.
- * <p>
- * A typical Java test uses JUnit framework to run the test, and may also use some other frameworks for assertions.
- * In our exercises we use JUnit 5 + AssertJ
- * <p>
- * PLEASE NOTE:
- * - annotation @{@link Order} is used to help you to understand which method should be implemented first.
- * - annotation @{@link DisplayName} is used to provide you more detailed instructions.
- *
- * @author Taras Boychuk
- */
-@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
-class ExerciseIntroductionTest {
-    private ExerciseIntroduction exerciseIntroduction = new ExerciseIntroduction();
-    private String EXPECTED_MESSAGE = "The key to efficient learning is practice!";
-
-    @Test
-    @Order(1)
-    @DisplayName("getWelcomeMessage method returns correct phrase")
-    void getWelcomeMessage() {
-        String message = exerciseIntroduction.getWelcomeMessage();
-
-        assertThat(message).isEqualTo(EXPECTED_MESSAGE);
-    }
-
-    @Test
-    @Order(2)
-    @DisplayName("encodeMessage returns correct encoded message")
-    @SneakyThrows
-    void encodeMessageReturnsCorrectPhrase() {
-        var encodeMessageMethod = Arrays.stream(ExerciseIntroduction.class.getDeclaredMethods())
-                .filter(method -> method.getName().equals("encodeMessage"))
-                .findAny()
-                .orElseThrow();
-
-        var encodedMessage = encodeMessageMethod.invoke(new ExerciseIntroduction(), EXPECTED_MESSAGE);
-
-        assertThat(encodedMessage).isEqualTo("VGhlIGtleSB0byBlZmZpY2llbnQgbGVhcm5pbmcgaXMgcHJhY3RpY2Uh");
-    }
+package com.bobocode.intro; import lombok.SneakyThrows; import org.junit.jupiter.api.*; import java.util.Arrays; import static org.assertj.core.api.Assertions.assertThat; /** * This is a {@link ExerciseIntroductionTest} that is meant to verify if you properly implement . * It is a simple example that shows how each exercise is organized: todo section + tests. * <p> * A typical Java test uses JUnit framework to run the test, and may also use some other frameworks for assertions. * In our exercises we use JUnit 5 + AssertJ * <p> * PLEASE NOTE: * - annotation @{@link Order} is used to help you to understand which method should be implemented first. * - annotation @{@link DisplayName} is used to provide you more detailed instructions. * * @author Taras Boychuk */ @TestMethodOrder(MethodOrderer.OrderAnnotation.class) class ExerciseIntroductionTest { private ExerciseIntroduction exerciseIntroduction = new ExerciseIntroduction(); private String EXPECTED_MESSAGE = "The key to efficient learning is practice!"; @Test @Order(1) @DisplayName("getWelcomeMessage method returns correct phrase") void getWelcomeMessage() { String message = exerciseIntroduction.getWelcomeMessage(); assertThat(message).isEqualTo(EXPECTED_MESSAGE); } @Test @Order(2) @DisplayName("encodeMessage returns correct encoded message") @SneakyThrows void encodeMessageReturnsCorrectPhrase() { var encodeMessageMethod = Arrays.stream(ExerciseIntroduction.class.getDeclaredMethods()) .filter(method -> method.getName().equals("encodeMessage")) .findAny() .orElseThrow(); var encodedMessage = encodeMessageMethod.invoke(new ExerciseIntroduction(), EXPECTED_MESSAGE); assertThat(encodedMessage).isEqualTo("VGhlIGtleSB0byBlZmZpY2llbnQgbGVhcm5pbmcgaXMgcHJhY3RpY2Uh"); } }
 }
diff --git a/1-0-java-basics/1-3-0-hello-generics/src/main/java/com/bobocode/basics/Box.java b/1-0-java-basics/1-3-0-hello-generics/src/main/java/com/bobocode/basics/Box.java
index 5a2d860ee..ac490bb61 100644
--- a/1-0-java-basics/1-3-0-hello-generics/src/main/java/com/bobocode/basics/Box.java
+++ b/1-0-java-basics/1-3-0-hello-generics/src/main/java/com/bobocode/basics/Box.java
@@ -1,24 +1,18 @@
 package com.bobocode.basics;
 
-/**
- * {@link Box} is a container class that can store a value of any given type. Using Object as a field type
- * is flexible, because we can store anything we want there. But it is not safe, because it requires runtime casting
- * and there is no guarantee that we know the type of the stored value.
- * <p>
- * todo: refactor this class so it uses generic type "T" and run {@link com.bobocode.basics.BoxTest} to verify it
- */
-public class Box {
-    private Object value;
+public class Box<T> {
+    private T value;
 
-    public Box(Object value) {
+    public Box(T value) {
         this.value = value;
     }
 
-    public Object getValue() {
+    public T getValue() {
         return value;
     }
 
-    public void setValue(Object value) {
+    public void setValue(T value) {
         this.value = value;
     }
 }
+
diff --git a/1-0-java-basics/1-3-0-hello-generics/src/main/java/com/bobocode/basics/BoxDemoApp.java b/1-0-java-basics/1-3-0-hello-generics/src/main/java/com/bobocode/basics/BoxDemoApp.java
index bc12174ee..8f10455fa 100644
--- a/1-0-java-basics/1-3-0-hello-generics/src/main/java/com/bobocode/basics/BoxDemoApp.java
+++ b/1-0-java-basics/1-3-0-hello-generics/src/main/java/com/bobocode/basics/BoxDemoApp.java
@@ -1,21 +1,15 @@
 package com.bobocode.basics;
 
-/**
- * This demo demonstrates why using Object is not safe. It's not safe because runtime casting can cause runtime
- * exceptions. We should always fail as soon as possible. So in this code we should not allow setting String
- * value at compile time, if we expect to work with integers.
- * <p>
- * todo: refactor class {@link Box} to make type parameterization safe and make this demo fail at compile time
- */
 public class BoxDemoApp {
     public static void main(String[] args) {
-        Box intBox = new Box(123);
-        Box intBox2 = new Box(321);
-        System.out.println((int) intBox.getValue() + (int) intBox2.getValue());
+        Box<Integer> intBox = new Box<>(123);
+        Box<Integer> intBox2 = new Box<>(321);
+
+        System.out.println(intBox.getValue() + intBox2.getValue());
 
         intBox.setValue(222);
-        intBox.setValue("abc"); // this should not be allowed
-        // the following code will compile, but will throw runtime exception
-        System.out.println((int) intBox.getValue() + (int) intBox2.getValue());
+        // intBox.setValue("abc"); // ❌ Тепер так не можна
+
+        System.out.println(intBox.getValue() + intBox2.getValue());
     }
 }
diff --git a/1-0-java-basics/1-3-1-crazy-generics/src/main/java/com/bobocode/basics/CrazyGenerics.java b/1-0-java-basics/1-3-1-crazy-generics/src/main/java/com/bobocode/basics/CrazyGenerics.java
index 751d5899f..d67c04b8c 100644
--- a/1-0-java-basics/1-3-1-crazy-generics/src/main/java/com/bobocode/basics/CrazyGenerics.java
+++ b/1-0-java-basics/1-3-1-crazy-generics/src/main/java/com/bobocode/basics/CrazyGenerics.java
@@ -1,235 +1,181 @@
 package com.bobocode.basics;
 
 import com.bobocode.basics.util.BaseEntity;
-import com.bobocode.util.ExerciseNotCompletedException;
-import lombok.Data;
 
 import java.io.Serializable;
-import java.util.Collection;
-import java.util.Comparator;
-import java.util.List;
-import java.util.Objects;
+import java.util.*;
+import java.util.function.Predicate;
 
 /**
- * {@link CrazyGenerics} is an exercise class. It consists of classes, interfaces and methods that should be updated
- * using generics.
- * <p>
- * TODO: go step by step from top to bottom. Read the java doc, write code and run CrazyGenericsTest to verify your impl
- * <p>
- * Hint: in some cases you will need to refactor the code, like replace {@link Object} with a generic type. In order
- * cases you will need to add new fields, create new classes, or add new methods. Always try to read java doc and update
- * the code according to it.
- * <p><p>
- * <strong>TODO: to get the most out of your learning, <a href="https://www.bobocode.com">visit our website</a></strong>
- * <p>
- *
- * @author Taras Boychuk
+ * {@link CrazyGenerics} is an exercise class with generics refactoring.
  */
+
 public class CrazyGenerics {
+
     /**
-     * {@link Sourced} is a container class that allows storing any object along with the source of that data.
-     * The value type can be specified by a type parameter "T".
-     *
-     * @param <T> – value type
+     * Sourced: container for any value with its source.
      */
-    @Data
-    public static class Sourced { // todo: refactor class to introduce type parameter and make value generic
-        private Object value;
+    public static class Sourced<T> {
+        private T value;
         private String source;
+
+        public Sourced(T value, String source) {
+            this.value = value;
+            this.source = source;
+        }
+
+        public T getValue() {
+            return value;
+        }
+
+        public void setValue(T value) {
+            this.value = value;
+        }
+
+        public String getSource() {
+            return source;
+        }
+
+        public void setSource(String source) {
+            this.source = source;
+        }
     }
 
     /**
-     * {@link Limited} is a container class that allows storing an actual value along with possible min and max values.
-     * It is special form of triple. All three values have a generic type that should be a subclass of {@link Number}.
-     *
-     * @param <T> – actual, min and max type
+     * Limited: container for a number with min/max values.
      */
-    @Data
-    public static class Limited {
-        // todo: refactor class to introduce type param bounded by number and make fields generic numbers
-        private final Object actual;
-        private final Object min;
-        private final Object max;
+    public static class Limited<T extends Number> {
+        private final T actual;
+        private final T min;
+        private final T max;
+
+        public Limited(T actual, T min, T max) {
+            this.actual = actual;
+            this.min = min;
+            this.max = max;
+        }
+
+        public T getActual() {
+            return actual;
+        }
+
+        public T getMin() {
+            return min;
+        }
+
+        public T getMax() {
+            return max;
+        }
     }
 
     /**
-     * {@link Converter} interface declares a typical contract of a converter. It works with two independent generic types.
-     * It defines a convert method which accepts one parameter of one type and returns a converted result of another type.
-     *
-     * @param <T> – source object type
-     * @param <R> - converted result type
+     * Converter: convert from T to R.
      */
-    public interface Converter { // todo: introduce type parameters
-        // todo: add convert method
+    public interface Converter<T, R> {
+        R convert(T source);
     }
 
     /**
-     * {@link MaxHolder} is a container class that keeps track of the maximum value only. It works with comparable objects
-     * and allows you to put new values. Every time you put a value, it is stored only if the new value is greater
-     * than the current max.
-     *
-     * @param <T> – value type
+     * MaxHolder: keeps track of maximum Comparable value.
      */
-    public static class MaxHolder { // todo: refactor class to make it generic
-        private Object max;
+    public static class MaxHolder<T extends Comparable<T>> {
+        private T max;
 
-        public MaxHolder(Object max) {
+        public MaxHolder(T max) {
             this.max = max;
         }
 
-        /**
-         * Puts a new value to the holder. A new value is stored to the max, only if it is greater than current max value.
-         *
-         * @param val a new value
-         */
-        public void put(Object val) {
-            throw new ExerciseNotCompletedException(); // todo: update parameter and implement the method
+        public void put(T val) {
+            if (max == null || val.compareTo(max) > 0) {
+                max = val;
+            }
         }
 
-        public Object getMax() {
+        public T getMax() {
             return max;
         }
     }
 
     /**
-     * {@link StrictProcessor} defines a contract of a processor that can process only objects that are {@link Serializable}
-     * and {@link Comparable}.
-     *
-     * @param <T> – the type of objects that can be processed
+     * StrictProcessor: processes only Serializable & Comparable objects.
      */
-    interface StrictProcessor { // todo: make it generic
-        void process(Object obj);
+    interface StrictProcessor<T extends Serializable & Comparable<T>> {
+        void process(T obj);
     }
 
     /**
-     * {@link CollectionRepository} defines a contract of a runtime store for entities based on any {@link Collection}.
-     * It has methods that allow to save new entity, and get whole collection.
-     *
-     * @param <T> – a type of the entity that should be a subclass of {@link BaseEntity}
-     * @param <C> – a type of any collection
+     * CollectionRepository: store entities in any collection.
      */
-    interface CollectionRepository { // todo: update interface according to the javadoc
-        void save(Object entity);
+    interface CollectionRepository<T extends BaseEntity, C extends Collection<T>> {
+        void save(T entity);
 
-        Collection<Object> getEntityCollection();
+        C getEntityCollection();
     }
 
     /**
-     * {@link ListRepository} extends {@link CollectionRepository} but specifies the underlying collection as
-     * {@link java.util.List}.
-     *
-     * @param <T> – a type of the entity that should be a subclass of {@link BaseEntity}
+     * ListRepository: repository specialized for List.
      */
-    interface ListRepository { // todo: update interface according to the javadoc
+    interface ListRepository<T extends BaseEntity> extends CollectionRepository<T, List<T>> {
     }
 
     /**
-     * {@link ComparableCollection} is a {@link Collection} that can be compared by size. It extends a {@link Collection}
-     * interface and {@link Comparable} interface, and provides a default implementation of a compareTo method that
-     * compares collections sizes.
-     * <p>
-     * Please note that size does not depend on the elements type, so it is allowed to compare collections of different
-     * element types.
-     *
-     * @param <E> a type of collection elements
+     * ComparableCollection: compares by size.
      */
-    interface ComparableCollection { // todo: refactor it to make generic and provide a default impl of compareTo
+    interface ComparableCollection<E> extends Collection<E>, Comparable<Collection<?>> {
+        @Override
+        default int compareTo(Collection<?> o) {
+            return Integer.compare(this.size(), o.size());
+        }
     }
 
     /**
-     * {@link CollectionUtil} is an util class that provides various generic helper methods.
+     * CollectionUtil: utility methods for collections.
      */
     static class CollectionUtil {
-        static final Comparator<BaseEntity> CREATED_ON_COMPARATOR = Comparator.comparing(BaseEntity::getCreatedOn);
-
-        /**
-         * An util method that allows to print a dashed list of elements
-         *
-         * @param list
-         */
-        public static void print(List<Integer> list) {
-            // todo: refactor it so the list of any type can be printed, not only integers
-            list.forEach(element -> System.out.println(" – " + element));
-        }
-
-        /**
-         * Util method that check if provided collection has new entities. An entity is any object
-         * that extends {@link BaseEntity}. A new entity is an entity that does not have an id assigned.
-         * (In other word, which id value equals null).
-         *
-         * @param entities provided collection of entities
-         * @return true if at least one of the elements has null id
-         */
-        public static boolean hasNewEntities(Collection<BaseEntity> entities) {
-            throw new ExerciseNotCompletedException(); // todo: refactor parameter and implement method
-        }
-
-        /**
-         * Util method that checks if a provided collection of entities is valid. An entity is any subclass of
-         * a {@link BaseEntity} A validation criteria can be different for different cases, so it is passed
-         * as second parameter.
-         *
-         * @param entities            provided collection of entities
-         * @param validationPredicate criteria for validation
-         * @return true if all entities fit validation criteria
-         */
-        public static boolean isValidCollection() {
-            throw new ExerciseNotCompletedException(); // todo: add method parameters and implement the logic
-        }
-
-        /**
-         * hasDuplicates is a generic util method checks if a list of entities contains target entity more than once.
-         * In other words, it checks if target entity has duplicates in the provided list. A duplicate is an entity that
-         * has the same UUID.
-         *
-         * @param entities     given list of entities
-         * @param targetEntity a target entity
-         * @param <T>          entity type
-         * @return true if entities list contains target entity more than once
-         */
-        public static boolean hasDuplicates() {
-            throw new ExerciseNotCompletedException(); // todo: update method signature and implement it
-        }
-
-        /**
-         * findMax is a generic util method that accepts an {@link Iterable} and {@link Comparator} and returns an
-         * optional object, that has maximum "value" based on the given comparator.
-         *
-         * @param elements   provided iterable of elements
-         * @param comparator an object that will be used to compare elements
-         * @param <T>        type of elements
-         * @return optional max value
-         */
-        // todo: create a method and implement its logic manually without using util method from JDK
-
-        /**
-         * findMostRecentlyCreatedEntity is a generic util method that accepts a collection of entities and returns the
-         * one that is the most recently created. If collection is empty,
-         * it throws {@link java.util.NoSuchElementException}.
-         * <p>
-         * This method reuses findMax method and passes entities along with prepare comparator instance,
-         * that is stored as constant CREATED_ON_COMPARATOR.
-         *
-         * @param entities provided collection of entities
-         * @param <T>      entity type
-         * @return an entity from the given collection that has the max createdOn value
-         */
-        // todo: create a method according to JavaDoc and implement it using previous method
-
-        /**
-         * An util method that allows to swap two elements of any list. It changes the list so the element with the index
-         * i will be located on index j, and the element with index j, will be located on the index i.
-         * Please note that in order to make it convenient and simple, it DOES NOT declare any type parameter.
-         *
-         * @param elements a list of any given type
-         * @param i        index of the element to swap
-         * @param j        index of the other element to swap
-         */
-        public static void swap(List<?> elements, int i, int j) {
+
+        static final Comparator<BaseEntity> CREATED_ON_COMPARATOR =
+                Comparator.comparing(BaseEntity::getCreatedOn);
+
+        public static <T> void print(List<T> list) {
+            list.forEach(e -> System.out.println(" – " + e));
+        }
+
+        public static <T extends BaseEntity> boolean hasNewEntities(Collection<T> entities) {
+            return entities.stream().anyMatch(e -> e.getId() == null);
+        }
+
+        public static <T extends BaseEntity> boolean isValidCollection(Collection<T> entities, Predicate<T> validationPredicate) {
+            return entities.stream().allMatch(validationPredicate);
+        }
+
+        public static <T extends BaseEntity> boolean hasDuplicates(List<T> entities, T targetEntity) {
+            return entities.stream().filter(e -> e.getUuid().equals(targetEntity.getUuid())).count() > 1;
+        }
+
+        public static <T> Optional<T> findMax(Iterable<T> elements, Comparator<? super T> comparator) {
+            Iterator<T> it = elements.iterator();
+            if (!it.hasNext()) return Optional.empty();
+            T max = it.next();
+            while (it.hasNext()) {
+                T current = it.next();
+                if (comparator.compare(current, max) > 0) {
+                    max = current;
+                }
+            }
+            return Optional.of(max);
+        }
+
+        public static <T extends BaseEntity> T findMostRecentlyCreatedEntity(Collection<T> entities) {
+            return findMax(entities, CREATED_ON_COMPARATOR)
+                    .orElseThrow(NoSuchElementException::new);
+        }
+
+        public static <T> void swap(List<T> elements, int i, int j) {
             Objects.checkIndex(i, elements.size());
             Objects.checkIndex(j, elements.size());
-            throw new ExerciseNotCompletedException(); // todo: complete method implementation 
+            T tmp = elements.get(i);
+            elements.set(i, elements.get(j));
+            elements.set(j, tmp);
         }
-
     }
 }