Merge pull request #871 from tochoromero/master
BAEL-7: Join and Split Collections
This commit is contained in:
Marek Lewandowski
GitHub
commit
0df0d3325f
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package org.baeldung.java.collections;
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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 java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.concurrent.atomic.AtomicInteger;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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import org.junit.Test;
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public class JoinSplitCollectionsUnitTest {
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@Test
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public void whenJoiningTwoArrays_thenJoined() {
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String[] animals1 = new String[] { "Dog", "Cat" };
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String[] animals2 = new String[] { "Bird", "Cow" };
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String[] result = Stream.concat(Arrays.stream(animals1), Arrays.stream(animals2))
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.toArray(String[]::new);
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assertArrayEquals(result, new String[] { "Dog", "Cat", "Bird", "Cow" });
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}
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@Test
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public void whenJoiningTwoCollections_thenJoined() {
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Collection<Integer> collection1 = Arrays.asList(7, 8, 9);
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Collection<Integer> collection2 = Arrays.asList(10, 11, 12);
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Collection<Integer> result = Stream.concat(collection1.stream(), collection2.stream())
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.collect(Collectors.toList());
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assertTrue(result.equals(Arrays.asList(7, 8, 9, 10, 11, 12)));
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}
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@Test
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public void whenJoiningTwoCollectionsWithFilter_thenJoined() {
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Collection<Integer> collection1 = Arrays.asList(7, 8, 11);
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Collection<Integer> collection2 = Arrays.asList(9, 12, 10);
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Collection<Integer> result = Stream.concat(collection1.stream(), collection2.stream())
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.filter(next -> next <= 10)
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.collect(Collectors.toList());
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assertTrue(result.equals(Arrays.asList(7, 8, 9, 10)));
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}
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@Test
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public void whenConvertArrayToString_thenConverted() {
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String[] colors = new String[] { "Red", "Blue", "Green", "Yellow" };
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String result = Arrays.stream(colors)
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.collect(Collectors.joining(", "));
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assertEquals(result, "Red, Blue, Green, Yellow");
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}
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@Test
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public void whenConvertCollectionToString_thenConverted() {
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Collection<String> directions = Arrays.asList("Left", "Right", "Top", "Bottom");
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String result = directions.stream()
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.collect(Collectors.joining(", "));
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assertEquals(result, "Left, Right, Top, Bottom");
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}
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@Test
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public void whenConvertMapToString_thenConverted() {
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Map<Integer, String> users = new HashMap<>();
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users.put(1, "John Doe");
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users.put(2, "Paul Smith");
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users.put(3, "Susan Anderson");
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String result = users.entrySet().stream().map(entry -> entry.getKey() + " = " + entry.getValue())
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.collect(Collectors.joining(", "));
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assertEquals(result, "1 = John Doe, 2 = Paul Smith, 3 = Susan Anderson");
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}
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@Test
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public void whenConvertNestedCollectionToString_thenConverted() {
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Collection<List<String>> nested = new ArrayList<>();
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nested.add(Arrays.asList("Left", "Right", "Top", "Bottom"));
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nested.add(Arrays.asList("Red", "Blue", "Green", "Yellow"));
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String result = nested.stream()
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.map(nextList -> nextList.stream()
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.collect(Collectors.joining("-")))
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.collect(Collectors.joining("; "));
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assertEquals(result, "Left-Right-Top-Bottom; Red-Blue-Green-Yellow");
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}
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@Test
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public void whenConvertCollectionToStringAndSkipNull_thenConverted() {
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Collection<String> fruits = Arrays.asList("Apple", "Orange", null, "Grape");
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String result = fruits.stream()
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.filter(next -> next != null)
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.collect(Collectors.joining(", "));
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assertEquals(result, "Apple, Orange, Grape");
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}
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@Test
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public void whenSplitCollectionHalf_thenConverted() {
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Collection<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
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Collection<Integer> result1 = new ArrayList<>();
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Collection<Integer> result2 = new ArrayList<>();
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AtomicInteger count = new AtomicInteger();
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int midpoint = Math.round(numbers.size() / 2);
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numbers.forEach(next -> {
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int index = count.getAndIncrement();
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if(index < midpoint){
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result1.add(next);
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}else{
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result2.add(next);
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}
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});
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assertTrue(result1.equals(Arrays.asList(1, 2, 3, 4, 5)));
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assertTrue(result2.equals(Arrays.asList(6, 7, 8, 9, 10)));
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}
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@Test
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public void whenSplitArrayByWordLength_thenConverted() {
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String[] words = new String[]{"bye", "cold", "it", "and", "my", "word"};
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Map<Integer, List<String>> result = Arrays.stream(words)
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.collect(Collectors.groupingBy(word -> word.length()));
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assertTrue(result.get(2).equals(Arrays.asList("it", "my")));
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assertTrue(result.get(3).equals(Arrays.asList("bye", "and")));
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assertTrue(result.get(4).equals(Arrays.asList("cold", "word")));
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}
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@Test
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public void whenConvertStringToArray_thenConverted() {
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String colors = "Red, Blue, Green, Yellow";
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String[] result = colors.split(", ");
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assertArrayEquals(result, new String[] { "Red", "Blue", "Green", "Yellow" });
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}
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@Test
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public void whenConvertStringToCollection_thenConverted() {
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String colors = "Left, Right, Top, Bottom";
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Collection<String> result = Arrays.asList(colors.split(", "));
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assertTrue(result.equals(Arrays.asList("Left", "Right", "Top", "Bottom")));
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}
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@Test
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public void whenConvertStringToMap_thenConverted() {
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String users = "1 = John Doe, 2 = Paul Smith, 3 = Susan Anderson";
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Map<Integer, String> result = Arrays.stream(users.split(", "))
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.map(next -> next.split(" = "))
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.collect(Collectors.toMap(entry -> Integer.parseInt(entry[0]), entry -> entry[1]));
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assertEquals(result.get(1), "John Doe");
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assertEquals(result.get(2), "Paul Smith");
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assertEquals(result.get(3), "Susan Anderson");
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}
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@Test
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public void whenConvertCollectionToStringMultipleSeparators_thenConverted() {
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String fruits = "Apple. , Orange, Grape. Lemon";
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Collection<String> result = Arrays.stream(fruits.split("[,|.]"))
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.map(String::trim)
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.filter(next -> !next.isEmpty())
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.collect(Collectors.toList());
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assertTrue(result.equals(Arrays.asList("Apple", "Orange", "Grape", "Lemon")));
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}
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}
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