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Refactor flattening lists example (#1372)

This commit is contained in:
Grzegorz Piwowarek 2017-03-18 07:05:02 +01:00 committed by GitHub
parent ac50687880
commit 99bebe806c
2 changed files with 44 additions and 49 deletions
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17
core-java/src/main/java/com/baeldung/list/flattennestedlist/FlattenNestedList.java
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@ -1,17 +0,0 @@
package com.baeldung.list.flattennestedlist;
import java.util.ArrayList;
import java.util.List;
public class FlattenNestedList {
public List<String> flattenListOfLists(List<List<String>> lol) {
// flatten the list
List<String> ls = new ArrayList<>();
lol.forEach((k) -> ls.addAll(k));
return ls;
}
}

76
core-java/src/test/java/com/baeldung/list/flattennestedlist/FlattenNestedListTest.java
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@ -1,52 +1,64 @@
package com.baeldung.list.flattennestedlist;
import org.junit.Test;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.stream.Collectors;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.junit.Before;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class FlattenNestedListTest {
private static final Logger LOGGER = LoggerFactory.getLogger(FlattenNestedListTest.class);
private FlattenNestedList flol;
@Before
public void setup() {
flol = new FlattenNestedList();
}
@Test
public void givenListOfListOfString_flattenNestedList() {
// create the list to flatten
public void givenListOfListOfString_flattenNestedList1() {
// given
List<String> ls1 = Arrays.asList("one:one", "one:two", "one:three");
List<String> ls2 = Arrays.asList("two:one", "two:two", "two:three");
List<String> ls3 = Arrays.asList("three:one", "three:two", "three:three");
List<List<String>> lol = new ArrayList<>();
lol.addAll(Arrays.asList(ls1, ls2, ls3));
// show nested list
LOGGER.debug("\nNested list: ");
lol.forEach((nl) -> LOGGER.debug(nl + ""));
List<List<String>> list = Arrays.asList(ls1, ls2, ls3);
// flatten it
List<String> ls = flol.flattenListOfLists(lol);
// when
List<String> ls = flattenListOfListsImperatively(list);
// then
assertNotNull(ls);
assertTrue(ls.size() == 9);
// show flattened list
LOGGER.debug("\nFlattened list:");
ls.forEach((l) -> LOGGER.debug(l));
//TODO content assertion
}
@Test
public void givenListOfListOfString_flattenNestedList2() {
// given
List<String> ls1 = Arrays.asList("one:one", "one:two", "one:three");
List<String> ls2 = Arrays.asList("two:one", "two:two", "two:three");
List<String> ls3 = Arrays.asList("three:one", "three:two", "three:three");
List<List<String>> list = Arrays.asList(ls1, ls2, ls3);
// when
List<String> ls = flattenListOfListsStream(list);
// then
assertNotNull(ls);
assertTrue(ls.size() == 9);
//TODO content assertion
}
public <T> List<T> flattenListOfListsImperatively(List<List<T>> list) {
List<T> ls = new ArrayList<>();
list.forEach(ls::addAll);
return ls;
}
public <T> List<T> flattenListOfListsStream(List<List<T>> list) {
return list.stream()
.flatMap(Collection::stream)
.collect(Collectors.toList());
}
}