From f421b5b40cfa0f21435c011da0a370bf374aa09c Mon Sep 17 00:00:00 2001 From: nehriienko Date: Thu, 9 Oct 2025 09:55:38 +0300 Subject: [PATCH 1/2] =?UTF-8?q?=20=D0=92=D0=B8=D0=BA=D0=BE=D0=BD=D0=B0?= =?UTF-8?q?=D0=BD=D1=96=20=D0=B7=D0=B0=D0=B2=D0=B4=D0=B0=D0=BD=D0=BD=D1=8F?= =?UTF-8?q?=20=D0=B7=20java-fundamentals-exercises?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../bobocode/intro/ExerciseIntroduction.java | 42 +++---------------- 1 file changed, 6 insertions(+), 36 deletions(-) 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..0dd7818f2 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 @@ -1,45 +1,15 @@ package com.bobocode.intro; -import com.bobocode.util.ExerciseNotCompletedException; +import java.util.Base64; + -/** - * Welcome! This is an introduction exercise that will show you a simple example of Bobocode exercises. - *

- * 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. - *

- * Every exercise is covered with tests, see {@link ExerciseIntroductionTest}. - *

- * 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}. - *

- * PLEASE NOTE THAT YOU WILL GET STUCK ON THIS METHOD INTENTIONALLY! ;) - *

- * 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 - throw new ExerciseNotCompletedException(); + return Base64.getEncoder().encodeToString(message.getBytes()); } -} +} \ No newline at end of file From 29c78be385086e7c60f5c3188ef26210861342f8 Mon Sep 17 00:00:00 2001 From: nehriienko Date: Thu, 23 Oct 2025 00:03:05 +0300 Subject: [PATCH 2/2] =?UTF-8?q?=20=D0=92=D0=B8=D0=BA=D0=BE=D0=BD=D0=B0?= =?UTF-8?q?=D0=BD=D1=96=20=D0=B7=D0=B0=D0=B2=D0=B4=D0=B0=D0=BD=D0=BD=D1=8F?= =?UTF-8?q?=20=D0=B7=20java-fundamentals-exercises?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../main/java/com/bobocode/basics/Box.java | 20 ++-- .../java/com/bobocode/basics/BoxDemoApp.java | 15 +-- .../com/bobocode/basics/CrazyGenerics.java | 102 +++++++++++------- 3 files changed, 76 insertions(+), 61 deletions(-) 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..9560ce387 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. - *

- * 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 Box(Object value) { +public class Box { + private T 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; } -} +} \ No newline at end of file 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..04c598f91 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 +1,14 @@ 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. - *

- * 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); + Box = new Box<>(123); + Box = new Box<>(321); System.out.println((int) intBox.getValue() + (int) intBox2.getValue()); intBox.setValue(222); - intBox.setValue("abc"); // this should not be allowed - // the following code will compile, but will throw runtime exception + intBox.setValue("abc"); System.out.println((int) intBox.getValue() + (int) 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..069a0bd6a 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 @@ -1,14 +1,12 @@ package com.bobocode.basics; import com.bobocode.basics.util.BaseEntity; -import com.bobocode.util.ExerciseNotCompletedException; import lombok.Data; +import lombok.val; 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 @@ -33,8 +31,8 @@ public class CrazyGenerics { * @param – 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 { // todo: refactor class to introduce type parameter and make value generic + private T value; private String source; } @@ -45,11 +43,11 @@ public static class Sourced { // todo: refactor class to introduce type paramete * @param – actual, min and max type */ @Data - public static class Limited { + 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; + private final T actual; + private final T min; + private final T max; } /** @@ -59,8 +57,8 @@ public static class Limited { * @param – source object type * @param - converted result type */ - public interface Converter { // todo: introduce type parameters - // todo: add convert method + public interface Converter { // todo: introduce type parameters + R convert(T obj); // todo: add convert method } /** @@ -70,10 +68,10 @@ public interface Converter { // todo: introduce type parameters * * @param – value type */ - public static class MaxHolder { // todo: refactor class to make it generic - private Object max; + public static class MaxHolder> { // todo: refactor class to make it generic + private T max; - public MaxHolder(Object max) { + public MaxHolder(T max) { this.max = max; } @@ -82,11 +80,13 @@ 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(max) > 0 ){ + max = val; // todo: update parameter and implement the method + } } - public Object getMax() { + public T getMax() { return max; } } @@ -97,8 +97,8 @@ public Object getMax() { * * @param – the type of objects that can be processed */ - interface StrictProcessor { // todo: make it generic - void process(Object obj); + interface StrictProcessor> { // todo: make it generic + void process(T obj); } /** @@ -108,10 +108,10 @@ interface StrictProcessor { // todo: make it generic * @param – a type of the entity that should be a subclass of {@link BaseEntity} * @param – a type of any collection */ - interface CollectionRepository { // todo: update interface according to the javadoc - void save(Object entity); + interface CollectionRepository> { // todo: update interface according to the javadoc + void save(T entity); - Collection getEntityCollection(); + C getEntityCollection(); } /** @@ -120,7 +120,7 @@ interface CollectionRepository { // todo: update interface according to the java * * @param – a type of the entity that should be a subclass of {@link BaseEntity} */ - interface ListRepository { // todo: update interface according to the javadoc + interface ListRepository extends CollectionRepository> { // todo: update interface according to the javadoc } /** @@ -133,7 +133,10 @@ interface ListRepository { // todo: update interface according to the javadoc * * @param a type of collection elements */ - interface ComparableCollection { // todo: refactor it to make generic and provide a default impl of compareTo + interface ComparableCollection extends Collection, Comparable> { + default int compareTo(Collection o){ + return Integer.compare(this.size(), o.size()); // todo: refactor it to make generic and provide a default impl of compareTo + } } /** @@ -147,7 +150,7 @@ static class CollectionUtil { * * @param list */ - public static void print(List list) { + public static void print(List list) { // todo: refactor it so the list of any type can be printed, not only integers list.forEach(element -> System.out.println(" – " + element)); } @@ -160,8 +163,9 @@ public static void print(List list) { * @param entities provided collection of entities * @return true if at least one of the elements has null id */ - public static boolean hasNewEntities(Collection entities) { - throw new ExerciseNotCompletedException(); // todo: refactor parameter and implement method + public static boolean hasNewEntities(Collection entities) { + return entities.stream() + .anyMatch(e ->e.getUuid() == null) ; // todo: refactor parameter and implement method } /** @@ -173,8 +177,10 @@ public static boolean hasNewEntities(Collection 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 entities, + Predicate validationPredicate) { + return entities.stream() + .allMatch(validationPredicate); // todo: add method parameters and implement the logic } /** @@ -187,8 +193,10 @@ public static boolean isValidCollection() { * @param 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 boolean hasDuplicates(Collection entities, T targetEntity) { + return entities.stream() + .filter(e -> e.getUuid().equals(targetEntity.getUuid())) + .count() > 1;// todo: update method signature and implement it } /** @@ -201,7 +209,20 @@ public static boolean hasDuplicates() { * @return optional max value */ // todo: create a method and implement its logic manually without using util method from JDK - + public static Optional findMax(Iterable elements, Comparator comparator) { + var iterator = elements.iterator(); + if (!iterator.hasNext()) { + return Optional.empty(); + } + var max = iterator.next(); + while (iterator.hasNext()) { + var element = iterator.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, @@ -215,7 +236,10 @@ public static boolean hasDuplicates() { * @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 findMostRecentlyCreatedEntity(Collection 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 * i will be located on index j, and the element with index j, will be located on the index i. @@ -228,8 +252,12 @@ 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 + swapHelper(elements, i, j); // todo: complete method implementation + } + private static void swapHelper(List elements, int i, int j) { + T temp = elements.get(i); + elements.set(i, elements.get(j)); + elements.set(j, temp); } - } }