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swapanpramanick2004pivovarit
swapanpramanick2004
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pivovarit
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BAEL-2178 (eugenp#5194)
* BAEL-2178 * revert previous commit, adding classes to collections project
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‎core-java-collections/src/main/java/com/baeldung/java/map/MapUtil.java‎

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

‎core-java-collections/src/test/java/com/baeldung/java/map/MapUtilUnitTest.java‎

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

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