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first pair code

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This commit is contained in:
akeshri
2020-09-08 21:04:43 +05:30
parent 93b8f878c8
commit 79fcbe173c
18 changed files with 182 additions and 499 deletions
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17
core-java-modules/core-java-collections-3/src/main/java/com/baeldung/collections/mapfirstpair/MapFirstPairService.java Normal file
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/**
*
*/
package com.baeldung.collections.mapfirstpair;
import java.util.Map;
/**
* @author ASHWINI
*
*/
public interface MapFirstPairService {
<K, V> Map.Entry<K, V> getFirstPairUsingIterator(Map<K, V> map);
<K, V> Map.Entry<K, V> getFirstPairUsingStream(Map<K, V> map);
}

40
core-java-modules/core-java-collections-3/src/main/java/com/baeldung/collections/mapfirstpair/MapFirstPairServiceImpl.java Normal file
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/**
*
*/
package com.baeldung.collections.mapfirstpair;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
/**
* @author ASHWINI
*
*/
public class MapFirstPairServiceImpl implements MapFirstPairService {
public <K, V> Map.Entry<K, V> getFirstPairUsingIterator(Map<K, V> map) {
if (map == null || map.size() == 0)
return null;
Iterator<Map.Entry<K, V>> iterator = map.entrySet()
.iterator();
if (iterator.hasNext())
return iterator.next();
return null;
}
public <K, V> Map.Entry<K, V> getFirstPairUsingStream(Map<K, V> map) {
if (map == null || map.size() == 0)
return null;
Set<Map.Entry<K, V>> entrySet = map.entrySet();
return entrySet.stream()
.findFirst()
.get();
}
}

125
core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/mapfirstpair/MapFirstPairServiceUnitTest.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.LinkedHashMap;
import java.util.Map;
import org.junit.Before;
import org.junit.Test;
public class MapFirstPairServiceUnitTest {
private MapFirstPairService mapFirstPairService;
@Before
public void Setup() {
mapFirstPairService = new MapFirstPairServiceImpl();
}
private void populateMapValues(Map<Integer, String> map) {
if (map != null) {
map.put(5, "A");
map.put(1, "B");
map.put(2, "C");
}
}
@Test
public void whenUsingIteratorForHashMap() {
Map<Integer, String> hashMap = new HashMap<>();
populateMapValues(hashMap);
Map.Entry<Integer, String> actualValue = mapFirstPairService.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() {
Map<Integer, String> hashMap = new HashMap<>();
populateMapValues(hashMap);
Map.Entry<Integer, String> actualValue = mapFirstPairService.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() {
Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
populateMapValues(linkedHashMap);
Map.Entry<Integer, String> actualValue = mapFirstPairService.getFirstPairUsingIterator(linkedHashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue);
}
@Test
public void whenUsingStreamForLinkedHashMap() {
Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
populateMapValues(linkedHashMap);
Map.Entry<Integer, String> actualValue = mapFirstPairService.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<>();
populateMapValues(hashMap);
hashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = mapFirstPairService.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<>();
populateMapValues(hashMap);
hashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = mapFirstPairService.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<>();
populateMapValues(linkedHashMap);
linkedHashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = mapFirstPairService.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<>();
populateMapValues(linkedHashMap);
linkedHashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = mapFirstPairService.getFirstPairUsingStream(linkedHashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue);
}
}