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This commit is contained in:
akeshri 2020-09-10 09:26:24 +05:30
parent ece4d65065
commit 2f91865363
2 changed files with 47 additions and 63 deletions
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42
core-java-modules/core-java-collections-3/src/main/java/com/baeldung/collections/mapfirstpair/MapFirstPairExample.java
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@ -1,42 +0,0 @@
package com.baeldung.collections.mapfirstpair;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
public class MapFirstPairExample {
public 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;
}
public 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();
}
public 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;
}
}

68
core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/mapfirstpair/MapFirstPairUnitTest.java
View File

@ -5,28 +5,54 @@ import static org.junit.Assert.assertNotEquals;
import java.util.AbstractMap; import java.util.AbstractMap;
import java.util.HashMap; import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap; import java.util.LinkedHashMap;
import java.util.Map; import java.util.Map;
import java.util.Set;
import org.junit.Before;
import org.junit.Test; import org.junit.Test;
public class MapFirstPairUnitTest { public class MapFirstPairUnitTest {
private MapFirstPairExample mapFirstPairExample; private Map.Entry<Integer, String> getFirstPairUsingIterator(Map<Integer, String> map) {
if (map == null || map.size() == 0)
return null;
@Before Iterator<Map.Entry<Integer, String>> iterator = map.entrySet()
public void Setup() { .iterator();
mapFirstPairExample = new MapFirstPairExample(); 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 @Test
public void whenUsingIteratorForHashMap_thenFirstPairWhichWasNotInsertedFirst() { public void whenUsingIteratorForHashMap_thenFirstPairWhichWasNotInsertedFirst() {
Map<Integer, String> hashMap = new HashMap<>(); Map<Integer, String> hashMap = new HashMap<>();
hashMap = mapFirstPairExample.populateMapValues(hashMap); hashMap = populateMapValues(hashMap);
Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingIterator(hashMap); Map.Entry<Integer, String> actualValue = getFirstPairUsingIterator(hashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(1, "B"); Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(1, "B");
Map.Entry<Integer, String> pairInsertedFirst = new AbstractMap.SimpleEntry<Integer, String>(5, "A"); Map.Entry<Integer, String> pairInsertedFirst = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
@ -37,8 +63,8 @@ public class MapFirstPairUnitTest {
@Test @Test
public void whenUsingStreamForHashMap_thenFirstPairWhichWasNotInsertedFirst() { public void whenUsingStreamForHashMap_thenFirstPairWhichWasNotInsertedFirst() {
Map<Integer, String> hashMap = new HashMap<>(); Map<Integer, String> hashMap = new HashMap<>();
hashMap = mapFirstPairExample.populateMapValues(hashMap); hashMap = populateMapValues(hashMap);
Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingStream(hashMap); Map.Entry<Integer, String> actualValue = getFirstPairUsingStream(hashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(1, "B"); Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(1, "B");
Map.Entry<Integer, String> pairInsertedFirst = new AbstractMap.SimpleEntry<Integer, String>(5, "A"); Map.Entry<Integer, String> pairInsertedFirst = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
@ -49,8 +75,8 @@ public class MapFirstPairUnitTest {
@Test @Test
public void whenUsingIteratorForLinkedHashMap_thenFirstPairWhichWasInsertedFirst() { public void whenUsingIteratorForLinkedHashMap_thenFirstPairWhichWasInsertedFirst() {
Map<Integer, String> linkedHashMap = new LinkedHashMap<>(); Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
linkedHashMap = mapFirstPairExample.populateMapValues(linkedHashMap); linkedHashMap = populateMapValues(linkedHashMap);
Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingIterator(linkedHashMap); Map.Entry<Integer, String> actualValue = getFirstPairUsingIterator(linkedHashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A"); Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue); assertEquals(expectedValue, actualValue);
@ -59,9 +85,9 @@ public class MapFirstPairUnitTest {
@Test @Test
public void whenUsingStreamForLinkedHashMap_thenFirstPairWhichWasInsertedFirst() { public void whenUsingStreamForLinkedHashMap_thenFirstPairWhichWasInsertedFirst() {
Map<Integer, String> linkedHashMap = new LinkedHashMap<>(); Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
linkedHashMap = mapFirstPairExample.populateMapValues(linkedHashMap); linkedHashMap = populateMapValues(linkedHashMap);
Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingStream(linkedHashMap); Map.Entry<Integer, String> actualValue = getFirstPairUsingStream(linkedHashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A"); Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue); assertEquals(expectedValue, actualValue);
@ -70,10 +96,10 @@ public class MapFirstPairUnitTest {
@Test @Test
public void whenAddedAnElementInHashMap_thenFirstPairChangedUsingIterator() { public void whenAddedAnElementInHashMap_thenFirstPairChangedUsingIterator() {
Map<Integer, String> hashMap = new HashMap<>(); Map<Integer, String> hashMap = new HashMap<>();
hashMap = mapFirstPairExample.populateMapValues(hashMap); hashMap = populateMapValues(hashMap);
hashMap.put(0, "D"); hashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingIterator(hashMap); Map.Entry<Integer, String> actualValue = getFirstPairUsingIterator(hashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(0, "D"); Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(0, "D");
assertEquals(expectedValue, actualValue); assertEquals(expectedValue, actualValue);
@ -82,10 +108,10 @@ public class MapFirstPairUnitTest {
@Test @Test
public void whenAddedAnElementInHashMap_thenFirstPairChangedUsingStream() { public void whenAddedAnElementInHashMap_thenFirstPairChangedUsingStream() {
Map<Integer, String> hashMap = new HashMap<>(); Map<Integer, String> hashMap = new HashMap<>();
hashMap = mapFirstPairExample.populateMapValues(hashMap); hashMap = populateMapValues(hashMap);
hashMap.put(0, "D"); hashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingStream(hashMap); Map.Entry<Integer, String> actualValue = getFirstPairUsingStream(hashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(0, "D"); Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(0, "D");
assertEquals(expectedValue, actualValue); assertEquals(expectedValue, actualValue);
@ -94,10 +120,10 @@ public class MapFirstPairUnitTest {
@Test @Test
public void whenAddedAnElementInLinkedHashMap_thenFirstPairRemainUnchangedUsingIterator() { public void whenAddedAnElementInLinkedHashMap_thenFirstPairRemainUnchangedUsingIterator() {
Map<Integer, String> linkedHashMap = new LinkedHashMap<>(); Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
linkedHashMap = mapFirstPairExample.populateMapValues(linkedHashMap); linkedHashMap = populateMapValues(linkedHashMap);
linkedHashMap.put(0, "D"); linkedHashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingIterator(linkedHashMap); Map.Entry<Integer, String> actualValue = getFirstPairUsingIterator(linkedHashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A"); Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue); assertEquals(expectedValue, actualValue);
@ -106,10 +132,10 @@ public class MapFirstPairUnitTest {
@Test @Test
public void whenAddedAnElementInLinkedHashMap_thenFirstPairRemainUnchangedUsingStream() { public void whenAddedAnElementInLinkedHashMap_thenFirstPairRemainUnchangedUsingStream() {
Map<Integer, String> linkedHashMap = new LinkedHashMap<>(); Map<Integer, String> linkedHashMap = new LinkedHashMap<>();
linkedHashMap = mapFirstPairExample.populateMapValues(linkedHashMap); linkedHashMap = populateMapValues(linkedHashMap);
linkedHashMap.put(0, "D"); linkedHashMap.put(0, "D");
Map.Entry<Integer, String> actualValue = mapFirstPairExample.getFirstPairUsingStream(linkedHashMap); Map.Entry<Integer, String> actualValue = getFirstPairUsingStream(linkedHashMap);
Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A"); Map.Entry<Integer, String> expectedValue = new AbstractMap.SimpleEntry<Integer, String>(5, "A");
assertEquals(expectedValue, actualValue); assertEquals(expectedValue, actualValue);