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Merge branch 'master' into BAEL-2977-stream-skip-limit
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‎algorithms-miscellaneous-3/src/main/java/com/baeldung/folding/FoldingHash.java‎

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package com.baeldung.folding;
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import java.util.stream.Collectors;
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import java.util.stream.IntStream;
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/**
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* Calculate a hash value for the strings using the folding technique.
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*
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* The implementation serves only to the illustration purposes and is far
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* from being the most efficient.
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*
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* @author A.Shcherbakov
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*
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*/
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public class FoldingHash {
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/**
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* Calculate the hash value of a given string.
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*
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* @param str Assume it is not null
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* @param groupSize the group size in the folding technique
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* @param maxValue defines a max value that the hash may acquire (exclusive)
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* @return integer value from 0 (inclusive) to maxValue (exclusive)
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*/
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public int hash(String str, int groupSize, int maxValue) {
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final int[] codes = this.toAsciiCodes(str);
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return IntStream.range(0, str.length())
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.filter(i -> i % groupSize == 0)
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.mapToObj(i -> extract(codes, i, groupSize))
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.map(block -> concatenate(block))
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.reduce(0, (a, b) -> (a + b) % maxValue);
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}
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/**
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* Returns a new array of given length whose elements are take from
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* the original one starting from the offset.
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*
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* If the original array has not enough elements, the returning array will contain
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* element from the offset till the end of the original array.
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*
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* @param numbers original array. Assume it is not null.
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* @param offset index of the element to start from. Assume it is less than the size of the array
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* @param length max size of the resulting array
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* @return
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*/
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public int[] extract(int[] numbers, int offset, int length) {
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final int defect = numbers.length - (offset + length);
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final int s = defect < 0 ? length + defect : length;
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int[] result = new int[s];
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for (int index = 0; index < s; index++) {
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result[index] = numbers[index + offset];
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}
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return result;
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}
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/**
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* Concatenate the numbers into a single number as if they were strings.
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* Assume that the procedure does not suffer from the overflow.
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* @param numbers integers to concatenate
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* @return
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*/
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public int concatenate(int[] numbers) {
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final String merged = IntStream.of(numbers)
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.mapToObj(number -> "" + number)
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.collect(Collectors.joining());
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return Integer.parseInt(merged, 10);
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}
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/**
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* Convert the string into its characters' ASCII codes.
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* @param str input string
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* @return
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*/
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private int[] toAsciiCodes(String str) {
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return str.chars()
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.toArray();
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}
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}

‎algorithms-miscellaneous-3/src/main/java/com/baeldung/folding/Main.java‎

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package com.baeldung.folding;
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/**
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* Code snippet for article "A Guide to the Folding Technique".
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*
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* @author A.Shcherbakov
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*
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*/
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public class Main {
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public static void main(String... arg) {
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FoldingHash hasher = new FoldingHash();
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final String str = "Java language";
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System.out.println(hasher.hash(str, 2, 100_000));
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System.out.println(hasher.hash(str, 3, 1_000));
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}
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}

‎algorithms-miscellaneous-3/src/test/java/com/baeldung/folding/FoldingHashUnitTest.java‎

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package com.baeldung.folding;
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import static org.junit.Assert.assertArrayEquals;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertTrue;
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import org.junit.Test;
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public class FoldingHashUnitTest {
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@Test
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public void givenStringJavaLanguage_whenSize2Capacity100000_then48933() throws Exception {
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final FoldingHash hasher = new FoldingHash();
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final int value = hasher.hash("Java language", 2, 100_000);
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assertEquals(value, 48933);
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}
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@Test
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public void givenStringVaJaLanguage_whenSize2Capacity100000_thenSameAsJavaLanguage() throws Exception {
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final FoldingHash hasher = new FoldingHash();
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final int java = hasher.hash("Java language", 2, 100_000);
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final int vaja = hasher.hash("vaJa language", 2, 100_000);
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assertTrue(java == vaja);
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}
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@Test
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public void givenSingleElementArray_whenOffset0Size2_thenSingleElement() throws Exception {
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final FoldingHash hasher = new FoldingHash();
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final int[] value = hasher.extract(new int[] { 5 }, 0, 2);
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assertArrayEquals(new int[] { 5 }, value);
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}
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@Test
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public void givenFiveElementArray_whenOffset0Size3_thenFirstThreeElements() throws Exception {
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final FoldingHash hasher = new FoldingHash();
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final int[] value = hasher.extract(new int[] { 1, 2, 3, 4, 5 }, 0, 3);
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assertArrayEquals(new int[] { 1, 2, 3 }, value);
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}
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@Test
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public void givenFiveElementArray_whenOffset1Size2_thenTwoElements() throws Exception {
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final FoldingHash hasher = new FoldingHash();
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final int[] value = hasher.extract(new int[] { 1, 2, 3, 4, 5 }, 1, 2);
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assertArrayEquals(new int[] { 2, 3 }, value);
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}
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@Test
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public void givenFiveElementArray_whenOffset2SizeTooBig_thenElementsToTheEnd() throws Exception {
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final FoldingHash hasher = new FoldingHash();
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final int[] value = hasher.extract(new int[] { 1, 2, 3, 4, 5 }, 2, 2000);
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assertArrayEquals(new int[] { 3, 4, 5 }, value);
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}
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}

core-java-modules/core-java-8-2/src/main/java/com/baeldung/delay/Delay.java renamed to core-java-modules/core-java-concurrency-basic/src/main/java/com/baeldung/concurrent/delay/Delay.java

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package com.baeldung.delay;
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package com.baeldung.concurrent.delay;
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import java.util.concurrent.Executors;
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import java.util.concurrent.ScheduledExecutorService;
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executorService.schedule(Delay::someTask1, delayInSeconds, TimeUnit.SECONDS);
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executorService.shutdown();
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}
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private static void fixedRateServiceTask(Integer delayInSeconds) {
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sf.cancel(true);
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executorService.shutdown();
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}
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private static void someTask1() {

‎core-java-modules/core-java-lambdas/README.md‎

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This file was deleted.

‎core-java-modules/core-java-nio/README.md‎

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## Relevant articles:
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- [Determine File Creating Date in Java](https://www.baeldung.com/file-creation-date-java)

‎core-java-modules/core-java-nio/src/main/java/com/baeldung/creationdate/CreationDateResolver.java‎

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package com.baeldung.creationdate;
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import java.io.IOException;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import java.nio.file.attribute.BasicFileAttributes;
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import java.nio.file.attribute.FileTime;
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import java.time.Instant;
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import java.util.Optional;
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public class CreationDateResolver {
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public Instant resolveCreationTimeWithBasicAttributes(Path path) {
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try {
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final BasicFileAttributes attr = Files.readAttributes(path, BasicFileAttributes.class);
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final FileTime fileTime = attr.creationTime();
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return fileTime.toInstant();
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} catch (IOException ex) {
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throw new RuntimeException("An issue occured went wrong when resolving creation time", ex);
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}
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}
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public Optional<Instant> resolveCreationTimeWithAttribute(Path path) {
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try {
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final FileTime creationTime = (FileTime) Files.getAttribute(path, "creationTime");
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return Optional
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.ofNullable(creationTime)
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.map((FileTime::toInstant));
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} catch (IOException ex) {
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throw new RuntimeException("An issue occured went wrong when resolving creation time", ex);
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}
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}
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}

‎core-java-modules/core-java-nio/src/test/java/com/baeldung/creationdate/CreationDateResolverUnitTest.java‎

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package com.baeldung.creationdate;
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import org.junit.Test;
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import java.io.File;
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import java.nio.file.Path;
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import java.time.Instant;
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import java.util.Optional;
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import static org.junit.Assert.assertTrue;
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public class CreationDateResolverUnitTest {
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private final CreationDateResolver creationDateResolver = new CreationDateResolver();
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@Test
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public void givenFile_whenGettingCreationDateTimeFromBasicAttributes_thenReturnDate() throws Exception {
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final File file = File.createTempFile("createdFile", ".txt");
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final Path path = file.toPath();
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final Instant response = creationDateResolver.resolveCreationTimeWithBasicAttributes(path);
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assertTrue(Instant
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.now()
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.isAfter(response));
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}
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@Test
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public void givenFile_whenGettingCreationDateTimeFromAttribute_thenReturnDate() throws Exception {
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final File file = File.createTempFile("createdFile", ".txt");
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final Path path = file.toPath();
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final Optional<Instant> response = creationDateResolver.resolveCreationTimeWithAttribute(path);
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response.ifPresent((value) -> {
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assertTrue(Instant
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.now()
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.isAfter(value));
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});
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}
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}

‎jackson-2/pom.xml‎

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<artifactId>jackson-dataformat-yaml</artifactId>
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<version>2.9.8</version>
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</dependency>
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<!-- CSV -->
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<dependency>
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<groupId>com.fasterxml.jackson.dataformat</groupId>
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<artifactId>jackson-dataformat-csv</artifactId>
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<version>2.9.8</version>
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</dependency>
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<!-- Allow use of LocalDate -->
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<dependency>

‎jackson-2/src/main/java/com/baeldung/jackson/csv/JsonCsvConverter.java‎

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package com.baeldung.jackson.csv;
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import java.io.File;
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import java.io.IOException;
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import com.baeldung.jackson.entities.OrderLine;
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import com.baeldung.jackson.mixin.OrderLineForCsv;
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import com.fasterxml.jackson.databind.JsonNode;
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import com.fasterxml.jackson.databind.MappingIterator;
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import com.fasterxml.jackson.databind.ObjectMapper;
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import com.fasterxml.jackson.databind.SerializationFeature;
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import com.fasterxml.jackson.dataformat.csv.CsvMapper;
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import com.fasterxml.jackson.dataformat.csv.CsvSchema;
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import com.fasterxml.jackson.dataformat.csv.CsvSchema.Builder;
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public class JsonCsvConverter {
17+
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public static void JsonToCsv(File jsonFile, File csvFile) throws IOException {
19+
JsonNode jsonTree = new ObjectMapper().readTree(jsonFile);
20+
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Builder csvSchemaBuilder = CsvSchema.builder();
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JsonNode firstObject = jsonTree.elements().next();
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firstObject.fieldNames().forEachRemaining(fieldName -> {csvSchemaBuilder.addColumn(fieldName);} );
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CsvSchema csvSchema = csvSchemaBuilder
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.build()
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.withHeader();
27+
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CsvMapper csvMapper = new CsvMapper();
29+
csvMapper.writerFor(JsonNode.class)
30+
.with(csvSchema)
31+
.writeValue(csvFile, jsonTree);
32+
}
33+
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public static void csvToJson(File csvFile, File jsonFile) throws IOException {
35+
CsvSchema orderLineSchema = CsvSchema.emptySchema().withHeader();
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CsvMapper csvMapper = new CsvMapper();
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MappingIterator<OrderLine> orderLines = csvMapper.readerFor(OrderLine.class)
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.with(orderLineSchema)
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.readValues(csvFile);
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new ObjectMapper()
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.configure(SerializationFeature.INDENT_OUTPUT, true)
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.writeValue(jsonFile, orderLines.readAll());
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}
45+
46+
public static void JsonToFormattedCsv(File jsonFile, File csvFile) throws IOException {
47+
CsvMapper csvMapper = new CsvMapper();
48+
CsvSchema csvSchema = csvMapper
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.schemaFor(OrderLineForCsv.class)
50+
.withHeader();
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csvMapper.addMixIn(OrderLine.class, OrderLineForCsv.class);
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53+
OrderLine[] orderLines = new ObjectMapper()
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.readValue(jsonFile, OrderLine[].class);
55+
csvMapper.writerFor(OrderLine[].class)
56+
.with(csvSchema)
57+
.writeValue(csvFile, orderLines);
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}
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}

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