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Виконані завдання з java-fundamentals-exercises #198

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View file Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
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.
Expand All @@ -23,23 +23,13 @@ public class ExerciseIntroduction {
* @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
throw new ExerciseNotCompletedException();
return Base64.getEncoder().encodeToString(message.getBytes());
}
}
View file Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,20 +5,19 @@
* 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;
}
}
View file Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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> { // todo: refactor class to introduce type parameter and make value generic
private T value;
private String source;
}

Expand All @@ -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;
}

/**
Expand All @@ -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 value);
}

/**
Expand All @@ -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<? super T>> {
private T max;

public MaxHolder(Object max) {
public MaxHolder(T max) {
this.max = max;
}

Expand All @@ -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(max) > 0) {
max = val;
}
}

public Object getMax() {
public T getMax() {
return max;
}
}
Expand All @@ -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<? super T>> {
void process(T obj);
}

/**
Expand All @@ -108,19 +107,21 @@ 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();
}


/**
* {@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}
*/
interface ListRepository { // todo: update interface according to the javadoc
interface ListRepository<T extends BaseEntity> extends CollectionRepository<T, List<T>> {

}

/**
Expand All @@ -133,7 +134,12 @@ 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<?> e) {
return Integer.compare(this.size(), e.size());
}
}

/**
Expand All @@ -147,8 +153,8 @@ 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));
}

Expand All @@ -160,8 +166,9 @@ 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);
}

/**
Expand All @@ -173,10 +180,13 @@ 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);
}


/**
* 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
Expand All @@ -187,8 +197,10 @@ 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;
}

/**
Expand All @@ -200,8 +212,21 @@ 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) {
Iterator<T> iterator = elements.iterator();
T max = iterator.next();

while (iterator.hasNext()) {
T current = iterator.next();

if (comparator.compare(current, max) > 0) {
max = current;
}
}

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,
Expand All @@ -214,7 +239,11 @@ 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
Expand All @@ -228,7 +257,13 @@ 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);
}

private static <T> void swapHelper(List<T> elements, int i, int j) {
T temp = elements.get(i);
elements.set(i, elements.get(j));
elements.set(j, temp);
}

}
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