Merging solutions

0-0-intro/src/main/java/com/bobocode/intro/Introduction.java

@@ -1,6 +1,7 @@
 package com.bobocode.intro;
 
-import com.bobocode.util.ExerciseNotCompletedException;
+
+import java.util.Base64;
 
 /**
  * Welcome! This is an introduction class that will show you a simple example of Bobocode exercise.
@@ -9,7 +10,7 @@
  * understand how to implement each method. So PLEASE MAKE SURE you read the Java Doc when start implementing a method.
  * <p>
  * Every exercise is covered with tests. So when you're implementing some class like {@link Introduction}, you should
- * also be able to find a corresponding class like {@link IntroductionTest}.
+ * also be able to find a corresponding class like {@link //IntroductionTest}.
  * <p>
  * Throughout the course you will need to implement hundreds of methods. And this is a simple example of how it's all
  * organized. You read the Java Doc, implement a method and run the test.
@@ -24,7 +25,7 @@ public class Introduction {
      * @return "The key to efficient learning is practice!"
      */
     public String getWelcomeMessage() {
-        throw new ExerciseNotCompletedException(); // todo: refactor it to return a message according to javadoc
+        return "The key to efficient learning is practice!";
     }
 
     /**
@@ -39,7 +40,6 @@ public String getWelcomeMessage() {
      * @return encoded message
      */
     public String encodeMessage(String message) {
-        // todo: switch to branch "completed" in order to see how it should be implemented
-        throw new ExerciseNotCompletedException();
+        return Base64.getEncoder().encodeToString(message.getBytes());
     }
 }

0-0-intro/src/test/java/com/bobocode/intro/IntroductionTest.java

@@ -31,7 +31,6 @@ class IntroductionTest {
     @DisplayName("getWelcomeMessage method returns correct phrase")
     void getWelcomeMessage() {
         String message = introduction.getWelcomeMessage();
-
         assertThat(message).isEqualTo(EXPECTED_MESSAGE);
     }
 

1-0-java-basics/1-3-0-hello-generics/src/main/java/com/bobocode/basics/Box.java

@@ -7,18 +7,19 @@
  * <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 Object value;
+    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;
     }
 }

1-0-java-basics/1-3-0-hello-generics/src/main/java/com/bobocode/basics/BoxDemoApp.java

@@ -9,13 +9,13 @@
  */
 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
+        //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());
+        System.out.println(intBox.getValue() + intBox2.getValue());
     }
 }

1-0-java-basics/1-3-1-crazy-generics/src/main/java/com/bobocode/basics/CrazyGenerics.java

@@ -5,10 +5,8 @@
 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
@@ -20,7 +18,7 @@
  * 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/learn">visit our website</a></strong>
+ * <strong>
  * <p>
  *
  * @author Taras Boychuk
@@ -33,8 +31,8 @@ public class CrazyGenerics {
      * @param <T> – value type
      */
     @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;
     }
 
@@ -45,11 +43,10 @@ public static class Sourced { // todo: refactor class to introduce type paramete
      * @param <T> – actual, min and max type
      */
     @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;
     }
 
     /**
@@ -59,8 +56,8 @@ public static class Limited {
      * @param <T> – source object type
      * @param <R> - converted result type
      */
-    public interface Converter { // todo: introduce type parameters
-        // todo: add convert method
+    public interface Converter<T, R>{
+         R convert(T t);
     }
 
     /**
@@ -70,10 +67,10 @@ public interface Converter { // todo: introduce type parameters
      *
      * @param <T> – value type
      */
-    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;
         }
 
@@ -82,11 +79,13 @@ public MaxHolder(Object max) {
          *
          * @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(val.compareTo(getMax()) > 0){
+                max = val;
+            }
         }
 
-        public Object getMax() {
+        public T getMax() {
             return max;
         }
     }
@@ -97,8 +96,8 @@ public Object getMax() {
      *
      * @param <T> – the type of objects that can be processed
      */
-    interface StrictProcessor { // todo: make it generic
-        void process(Object obj);
+    interface StrictProcessor<T extends Serializable & Comparable<T>> {
+        void process(T t);
     }
 
     /**
@@ -108,10 +107,10 @@ interface StrictProcessor { // todo: make it generic
      * @param <T> – a type of the entity that should be a subclass of {@link BaseEntity}
      * @param <C> – a type of 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();
     }
 
     /**
@@ -120,7 +119,7 @@ interface CollectionRepository { // todo: update interface according to the java
      *
      * @param <T> – a type of the entity that should be a subclass of {@link BaseEntity}
      */
-    interface ListRepository { // todo: update interface according to the javadoc
+    interface ListRepository<T extends BaseEntity> extends CollectionRepository<T, List<T>> {
     }
 
     /**
@@ -133,7 +132,11 @@ interface ListRepository { // todo: update interface according to the javadoc
      *
      * @param <E> a type of collection elements
      */
-    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());
+        }
     }
 
     /**
@@ -147,8 +150,7 @@ static class CollectionUtil {
          *
          * @param list
          */
-        public static void print(List<Integer> list) {
-            // todo: refactor it so the list of any type can be printed, not only integers
+        public static void print(List<?> list) {
             list.forEach(element -> System.out.println(" – " + element));
         }
 
@@ -160,8 +162,9 @@ public static void print(List<Integer> list) {
          * @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
+        public static boolean hasNewEntities(Collection<? extends BaseEntity> entities) {
+            return entities.stream()
+                    .anyMatch(e -> e.getUuid() == null);
         }
 
         /**
@@ -173,8 +176,9 @@ public static boolean hasNewEntities(Collection<BaseEntity> 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
+        public static boolean isValidCollection(Collection<? extends BaseEntity> entities, Predicate<? super BaseEntity> validationPredicate) {
+            return entities.stream()
+                    .allMatch(validationPredicate);
         }
 
         /**
@@ -187,8 +191,10 @@ public static boolean isValidCollection() {
          * @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
+        public static <T extends BaseEntity> boolean hasDuplicates(Collection<T> entities, T targetEntity) {
+            return entities.stream()
+                    .filter(e -> e.getUuid().equals(targetEntity.getUuid()))
+                    .count() > 1;
         }
 
         /**
@@ -200,8 +206,21 @@ public static boolean hasDuplicates() {
          * @param <T>        type of elements
          * @return optional max value
          */
-        // todo: create a method and implement its logic manually without using util method from JDK
 
+        public static <T> Optional<T> findMax (Iterable<T> elements, Comparator<? super T> comparator){
+            var it = elements.iterator();
+            if (!it.hasNext()){
+                return Optional.empty();
+            }
+            var max = it.next();
+            while (it.hasNext()){
+                var element = it.next();
+                if (comparator.compare(element, max) > 0){
+                    max = element;
+                }
+            }
+            return Optional.of(max);
+        }
         /**
          * 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,
@@ -214,7 +233,10 @@ public static boolean hasDuplicates() {
          * @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
+        public static <T extends BaseEntity> T findMostRecentlyCreatedEntity(Collection<T> entities){
+            return findMax(entities, CREATED_ON_COMPARATOR)
+                    .orElseThrow();
+        }
 
         /**
          * An util method that allows to swap two elements of any list. It changes the list so the element with the index
@@ -228,8 +250,12 @@ public static boolean hasDuplicates() {
         public static void swap(List<?> elements, int i, int j) {
             Objects.checkIndex(i, elements.size());
             Objects.checkIndex(j, elements.size());
-            throw new ExerciseNotCompletedException(); // todo: complete method implementation 
+            swaper(elements, i, j);
+        }
+        private static <T> void swaper(List<T> elements, int i, int j){
+            T temp = elements.get(i);
+            elements.set(i,elements.get(j));
+            elements.set(j,temp);
         }
-
     }
 }

1-0-java-basics/1-5-0-hello-annotations/src/main/java/com/bobocode/basics/Exercise.java

@@ -0,0 +1,14 @@
+package com.bobocode.basics;
+
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Exercise {
+    String value();
+    Level complexityLevel() default Level.BASIC;
+}

1-0-java-basics/1-5-0-hello-annotations/src/main/java/com/bobocode/basics/HelloAnnotationsExercise.java

@@ -13,5 +13,6 @@
  *
  * @author Taras Boychuk
  */
-public class HelloAnnotationsExercise { // todo: mark class with the annotation according to the javadoc
+@Exercise("hello-annotation-basic")
+public class HelloAnnotationsExercise {
 }

2-0-data-structures-and-algorithms/2-2-1-node/src/main/java/com/bobobode/cs/Node.java

@@ -9,5 +9,10 @@
  * @author Taras Boychuk
  */
 public class Node<T> {
-    // todo:
+    T element = null;
+    Node<T> next = null;
+
+    public Node(T element) {
+        this.element = element;
+    }
 }