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Merge pull request #9941 from akeshri/master 

BAEL-4383 : HashMap - getting First Key value
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bfontana 2020-09-10 21:18:27 -03:00 committed by GitHub
parent ed8b77a375 2f91865363
commit 7b11eeb69b
1 changed files with 143 additions and 0 deletions
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core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/mapfirstpair/MapFirstPairUnitTest.java Normal file
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package com.baeldung.collections.mapfirstpair;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotEquals;
import java.util.AbstractMap;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import org.junit.Test;
public class MapFirstPairUnitTest {
private Map.Entry<Integer, String> getFirstPairUsingIterator(Map<Integer, String> map) {
if (map == null || map.size() == 0)
return null;
Iterator<Map.Entry<Integer, String>> iterator = map.entrySet()
.iterator();
if (iterator.hasNext())
return iterator.next();
return null;
}
private Map.Entry<Integer, String> getFirstPairUsingStream(Map<Integer, String> map) {
if (map == null || map.size() == 0)
return null;
Set<Map.Entry<Integer, String>> entrySet = map.entrySet();
return entrySet.stream()
.findFirst()
.get();
}
private Map<Integer, String> populateMapValues(Map<Integer, String> map) {
if (map != null) {
map.put(5, "A");
map.put(1, "B");
map.put(2, "C");
}
return map;
}
@Test
public void whenUsingIteratorForHashMap_thenFirstPairWhichWasNotInsertedFirst() {
Map<Integer, String> hashMap = new HashMap<>();
hashMap = populateMapValues(hashMap);
Map.Entry<Integer, String> actualValue = getFirstPairUsingIterator(hashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(1, "B");
Map.Entry<Integer, String> pairInsertedFirst = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue);
assertNotEquals(pairInsertedFirst, actualValue);
}
@Test
public void whenUsingStreamForHashMap_thenFirstPairWhichWasNotInsertedFirst() {
Map<Integer, String> hashMap = new HashMap<>();
hashMap = populateMapValues(hashMap);
Map.Entry<Integer, String> actualValue = getFirstPairUsingStream(hashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(1, "B");
Map.Entry<Integer, String> pairInsertedFirst = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue);
assertNotEquals(pairInsertedFirst, actualValue);
}
@Test
public void whenUsingIteratorForLinkedHashMap_thenFirstPairWhichWasInsertedFirst() {
Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
linkedHashMap = populateMapValues(linkedHashMap);
Map.Entry<Integer, String> actualValue = getFirstPairUsingIterator(linkedHashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue);
}
@Test
public void whenUsingStreamForLinkedHashMap_thenFirstPairWhichWasInsertedFirst() {
Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
linkedHashMap = populateMapValues(linkedHashMap);
Map.Entry<Integer, String> actualValue = getFirstPairUsingStream(linkedHashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue);
}
@Test
public void whenAddedAnElementInHashMap_thenFirstPairChangedUsingIterator() {
Map<Integer, String> hashMap = new HashMap<>();
hashMap = populateMapValues(hashMap);
hashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = getFirstPairUsingIterator(hashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(0, "D");
assertEquals(expectedValue, actualValue);
}
@Test
public void whenAddedAnElementInHashMap_thenFirstPairChangedUsingStream() {
Map<Integer, String> hashMap = new HashMap<>();
hashMap = populateMapValues(hashMap);
hashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = getFirstPairUsingStream(hashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(0, "D");
assertEquals(expectedValue, actualValue);
}
@Test
public void whenAddedAnElementInLinkedHashMap_thenFirstPairRemainUnchangedUsingIterator() {
Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
linkedHashMap = populateMapValues(linkedHashMap);
linkedHashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = getFirstPairUsingIterator(linkedHashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue);
}
@Test
public void whenAddedAnElementInLinkedHashMap_thenFirstPairRemainUnchangedUsingStream() {
Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
linkedHashMap = populateMapValues(linkedHashMap);
linkedHashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = getFirstPairUsingStream(linkedHashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue);
}
}