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akeshriakeshri
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‎core-java-modules/core-java-collections-3/src/main/java/com/baeldung/collections/mapfirstpair/MapFirstPairExample.java‎

Lines changed: 42 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,42 @@
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package com.baeldung.collections.mapfirstpair;
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import java.util.Iterator;
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import java.util.Map;
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import java.util.Set;
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public class MapFirstPairExample {
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public Map.Entry<Integer, String> getFirstPairUsingIterator(Map<Integer, String> map) {
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if (map == null || map.size() == 0)
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return null;
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Iterator<Map.Entry<Integer, String>> iterator = map.entrySet()
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.iterator();
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if (iterator.hasNext())
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return iterator.next();
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return null;
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}
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public Map.Entry<Integer, String> getFirstPairUsingStream(Map<Integer, String> map) {
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if (map == null || map.size() == 0)
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return null;
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Set<Map.Entry<Integer, String>> entrySet = map.entrySet();
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return entrySet.stream()
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.findFirst()
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.get();
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}
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public Map<Integer, String> populateMapValues(Map<Integer, String> map) {
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if (map != null) {
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map.put(5, "A");
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map.put(1, "B");
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map.put(2, "C");
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}
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return map;
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}
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}

‎core-java-modules/core-java-collections-3/src/main/java/com/baeldung/collections/mapfirstpair/MapFirstPairService.java‎

Lines changed: 0 additions & 17 deletions
This file was deleted.

‎core-java-modules/core-java-collections-3/src/main/java/com/baeldung/collections/mapfirstpair/MapFirstPairServiceImpl.java‎

Lines changed: 0 additions & 40 deletions
This file was deleted.

core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/mapfirstpair/MapFirstPairServiceUnitTest.java renamed to core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/mapfirstpair/MapFirstPairUnitTest.java

Lines changed: 23 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -11,30 +11,22 @@
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import org.junit.Before;
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import org.junit.Test;
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public class MapFirstPairServiceUnitTest {
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public class MapFirstPairUnitTest {
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private MapFirstPairService mapFirstPairService;
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private MapFirstPairExample mapFirstPairExample;
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@Before
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public void Setup() {
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21-
mapFirstPairService = new MapFirstPairServiceImpl();
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}
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private void populateMapValues(Map<Integer, String> map) {
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if (map != null) {
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map.put(5, "A");
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map.put(1, "B");
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map.put(2, "C");
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}
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mapFirstPairExample = new MapFirstPairExample();
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}
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@Test
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public void whenUsingIteratorForHashMap() {
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public void whenUsingIteratorForHashMap_thenFirstPairWhichWasNotInsertedFirst() {
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Map<Integer, String> hashMap = new HashMap<>();
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populateMapValues(hashMap);
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hashMap = mapFirstPairExample.populateMapValues(hashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairService.getFirstPairUsingIterator(hashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingIterator(hashMap);
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Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(1, "B");
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Map.Entry<Integer, String> pairInsertedFirst = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
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@@ -43,10 +35,10 @@ public void whenUsingIteratorForHashMap() {
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}
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@Test
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public void whenUsingStreamForHashMap() {
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public void whenUsingStreamForHashMap_thenFirstPairWhichWasNotInsertedFirst() {
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Map<Integer, String> hashMap = new HashMap<>();
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populateMapValues(hashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairService.getFirstPairUsingStream(hashMap);
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hashMap = mapFirstPairExample.populateMapValues(hashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingStream(hashMap);
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Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(1, "B");
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Map.Entry<Integer, String> pairInsertedFirst = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
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@@ -55,21 +47,21 @@ public void whenUsingStreamForHashMap() {
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}
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5749
@Test
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public void whenUsingIteratorForLinkedHashMap() {
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public void whenUsingIteratorForLinkedHashMap_thenFirstPairWhichWasInsertedFirst() {
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Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
60-
populateMapValues(linkedHashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairService.getFirstPairUsingIterator(linkedHashMap);
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linkedHashMap = mapFirstPairExample.populateMapValues(linkedHashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingIterator(linkedHashMap);
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Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
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6456
assertEquals(expectedValue, actualValue);
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}
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@Test
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public void whenUsingStreamForLinkedHashMap() {
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public void whenUsingStreamForLinkedHashMap_thenFirstPairWhichWasInsertedFirst() {
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Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
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populateMapValues(linkedHashMap);
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linkedHashMap = mapFirstPairExample.populateMapValues(linkedHashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairService.getFirstPairUsingStream(linkedHashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingStream(linkedHashMap);
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Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
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assertEquals(expectedValue, actualValue);
@@ -78,10 +70,10 @@ public void whenUsingStreamForLinkedHashMap() {
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@Test
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public void whenAddedAnElementInHashMap_thenFirstPairChangedUsingIterator() {
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Map<Integer, String> hashMap = new HashMap<>();
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populateMapValues(hashMap);
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hashMap = mapFirstPairExample.populateMapValues(hashMap);
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hashMap.put(0, "D");
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Map.Entry<Integer, String> actualValue = mapFirstPairService.getFirstPairUsingIterator(hashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingIterator(hashMap);
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Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(0, "D");
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8779
assertEquals(expectedValue, actualValue);
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@Test
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public void whenAddedAnElementInHashMap_thenFirstPairChangedUsingStream() {
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Map<Integer, String> hashMap = new HashMap<>();
93-
populateMapValues(hashMap);
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hashMap = mapFirstPairExample.populateMapValues(hashMap);
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hashMap.put(0, "D");
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Map.Entry<Integer, String> actualValue = mapFirstPairService.getFirstPairUsingStream(hashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingStream(hashMap);
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Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(0, "D");
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9991
assertEquals(expectedValue, actualValue);
@@ -102,10 +94,10 @@ public void whenAddedAnElementInHashMap_thenFirstPairChangedUsingStream() {
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@Test
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public void whenAddedAnElementInLinkedHashMap_thenFirstPairRemainUnchangedUsingIterator() {
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Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
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populateMapValues(linkedHashMap);
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linkedHashMap = mapFirstPairExample.populateMapValues(linkedHashMap);
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10799
linkedHashMap.put(0, "D");
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Map.Entry<Integer, String> actualValue = mapFirstPairService.getFirstPairUsingIterator(linkedHashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingIterator(linkedHashMap);
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Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
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111103
assertEquals(expectedValue, actualValue);
@@ -114,10 +106,10 @@ public void whenAddedAnElementInLinkedHashMap_thenFirstPairRemainUnchangedUsingI
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@Test
115107
public void whenAddedAnElementInLinkedHashMap_thenFirstPairRemainUnchangedUsingStream() {
116108
Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
117-
populateMapValues(linkedHashMap);
109+
linkedHashMap = mapFirstPairExample.populateMapValues(linkedHashMap);
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119111
linkedHashMap.put(0, "D");
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Map.Entry<Integer, String> actualValue = mapFirstPairService.getFirstPairUsingStream(linkedHashMap);
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Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingStream(linkedHashMap);
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Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
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123115
assertEquals(expectedValue, actualValue);

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