iSharkFly-Docs
/
java-tutorials
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

BAEL-2178 (#5194) 

* BAEL-2178

* revert previous commit, adding classes to collections project
This commit is contained in:
Swapan Pramanick 2018-09-11 09:26:33 +05:30 committed by Grzegorz Piwowarek
parent 57b6480e73
commit fe96e112a5
2 changed files with 148 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
core-java-collections/src/main/java/com/baeldung/java/map/MapUtil.java Normal file
View File

@ -0,0 +1,44 @@
/**
*
*/
package com.baeldung.java.map;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
import java.util.stream.Stream;
/**
* @author swpraman
*
*/
public class MapUtil {
public static <K, V> Stream<K> keys(Map<K, V> map, V value) {
return map.entrySet()
.stream()
.filter(entry -> value.equals(entry.getValue()))
.map(Map.Entry::getKey);
}
public static <K, V> Set<K> getKeys(Map<K, V> map, V value) {
Set<K> keys = new HashSet<>();
for (Entry<K, V> entry : map.entrySet()) {
if (entry.getValue().equals(value)) {
keys.add(entry.getKey());
}
}
return keys;
}
public static <K, V> K getKey(Map<K, V> map, V value) {
for (Entry<K, V> entry : map.entrySet()) {
if (entry.getValue().equals(value)) {
return entry.getKey();
}
}
return null;
}
}

104
core-java-collections/src/test/java/com/baeldung/java/map/MapUtilUnitTest.java Normal file
View File

@ -0,0 +1,104 @@
/**
*
*/
package com.baeldung.java.map;
import static org.junit.Assert.assertEquals;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.stream.Collectors;
import org.apache.commons.collections4.BidiMap;
import org.apache.commons.collections4.bidimap.DualHashBidiMap;
import org.junit.Test;
import com.google.common.collect.HashBiMap;
/**
* @author swpraman
*
*/
public class MapUtilUnitTest {
@Test
public void whenUsingImperativeWayForSingleKey_shouldReturnSingleKey() {
Map<String, String> capitalCountryMap = new HashMap<>();
capitalCountryMap.put("Tokyo", "Japan");
capitalCountryMap.put("New Delhi", "India");
assertEquals("New Delhi", MapUtil.getKey(capitalCountryMap, "India"));
}
@Test
public void whenUsingImperativeWayForAllKeys_shouldReturnAllKeys() {
Map<String, String> capitalCountryMap = new HashMap<>();
capitalCountryMap.put("Tokyo", "Japan");
capitalCountryMap.put("Berlin", "Germany");
capitalCountryMap.put("Cape Town", "South Africa");
capitalCountryMap.put("Pretoria", "South Africa");
capitalCountryMap.put("Bloemfontein", "South Africa");
assertEquals(new HashSet<String>(Arrays.asList(
new String[] {"Cape Town", "Pretoria", "Bloemfontein"})),
MapUtil.getKeys(capitalCountryMap, "South Africa"));
}
@Test
public void whenUsingFunctionalWayForSingleKey_shouldReturnSingleKey() {
Map<String, String> capitalCountryMap = new HashMap<>();
capitalCountryMap.put("Tokyo", "Japan");
capitalCountryMap.put("Berlin", "Germany");
assertEquals("Berlin", MapUtil.keys(capitalCountryMap, "Germany").findFirst().get());
}
@Test
public void whenUsingFunctionalWayForAllKeys_shouldReturnAllKeys() {
Map<String, String> capitalCountryMap = new HashMap<>();
capitalCountryMap.put("Tokyo", "Japan");
capitalCountryMap.put("Berlin", "Germany");
capitalCountryMap.put("Cape Town", "South Africa");
capitalCountryMap.put("Pretoria", "South Africa");
capitalCountryMap.put("Bloemfontein", "South Africa");
assertEquals(new HashSet<String>(Arrays.asList(
new String[] {"Cape Town", "Pretoria", "Bloemfontein"})),
MapUtil.keys(capitalCountryMap, "South Africa").collect(Collectors.toSet()));
}
@Test
public void whenUsingBidiMap_shouldReturnKey() {
BidiMap<String, String> capitalCountryMap = new DualHashBidiMap<String, String>();
capitalCountryMap.put("Berlin", "Germany");
capitalCountryMap.put("Cape Town", "South Africa");
assertEquals("Berlin", capitalCountryMap.getKey("Germany"));
}
@Test
public void whenUsingBidiMapAddDuplicateValue_shouldRemoveOldEntry() {
BidiMap<String, String> capitalCountryMap = new DualHashBidiMap<String, String>();
capitalCountryMap.put("Berlin", "Germany");
capitalCountryMap.put("Cape Town", "South Africa");
capitalCountryMap.put("Pretoria", "South Africa");
assertEquals("Pretoria", capitalCountryMap.getKey("South Africa"));
}
@Test
public void whenUsingBiMap_shouldReturnKey() {
HashBiMap<String, String> capitalCountryMap = HashBiMap.create();
capitalCountryMap.put("Berlin", "Germany");
capitalCountryMap.put("Cape Town", "South Africa");
assertEquals("Berlin", capitalCountryMap.inverse().get("Germany"));
}
@Test(expected=IllegalArgumentException.class)
public void whenUsingBiMapAddDuplicateValue_shouldThrowException() {
HashBiMap<String, String> capitalCountryMap = HashBiMap.create();
capitalCountryMap.put("Berlin", "Germany");
capitalCountryMap.put("Cape Town", "South Africa");
capitalCountryMap.put("Pretoria", "South Africa");
assertEquals("Berlin", capitalCountryMap.inverse().get("Germany"));
}
}