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Revert "BAEL-5348: Invert a Map in Java + tests"

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This reverts commit 3dd2802e2db7ad12994e16e79aa2a4ca2dadc202.
This commit is contained in:
Palaniappan Arunachalam 2022-02-09 13:26:47 +05:30
parent 3d6e3af927
commit e4c615b522
2 changed files with 0 additions and 119 deletions
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59
java-collections-maps-3/src/main/java/com/baeldung/map/invert/InvertHashMapExample.java
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package com.baeldung.map.invert;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.stream.Collectors;
public class InvertHashMapExample {
public static void main(String[] args) {
Map<String, Integer> map = new HashMap<>();
map.put("first", 1);
map.put("second", 2);
System.out.println(map);
invertMapUsingForLoop(map);
invertMapUsingStreams(map);
invertMapUsingMapper(map);
map.put("two", 2);
invertMapUsingGroupingBy(map);
}
public static <V, K> Map<V, K> invertMapUsingForLoop(Map<K, V> map) {
Map<V, K> inversedMap = new HashMap<V, K>();
for (Entry<K, V> entry : map.entrySet()) {
inversedMap.put(entry.getValue(), entry.getKey());
}
System.out.println(inversedMap);
return inversedMap;
}
public static <V, K> Map<V, K> invertMapUsingStreams(Map<K, V> map) {
Map<V, K> inversedMap = map.entrySet()
.stream()
.collect(Collectors.toMap(Entry::getValue, Entry::getKey));
System.out.println(inversedMap);
return inversedMap;
}
public static <K, V> Map<V, K> invertMapUsingMapper(Map<K, V> sourceMap) {
Map<V, K> inversedMap = sourceMap.entrySet()
.stream()
.collect(Collectors.toMap(Entry::getValue, Entry::getKey, (oldValue, newValue) -> oldValue));
System.out.println(inversedMap);
return inversedMap;
}
public static <V, K> Map<V, List<K>> invertMapUsingGroupingBy(Map<K, V> map) {
Map<V, List<K>> inversedMap = map.entrySet()
.stream()
.collect(Collectors.groupingBy(Map.Entry::getValue, Collectors.mapping(Map.Entry::getKey, Collectors.toList())));
System.out.println(inversedMap);
return inversedMap;
}
}

60
java-collections-maps-3/src/test/java/com/baeldung/map/invert/InvertHashMapExampleTest.java
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@ -1,60 +0,0 @@
package com.baeldung.map.invert;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;
import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInstance;
@TestInstance(TestInstance.Lifecycle.PER_CLASS)
public class InvertHashMapExampleTest {
Map<String, Integer> sourceMap;
@BeforeAll
void setup() {
sourceMap = new HashMap<>();
sourceMap.put("Sunday", 0);
sourceMap.put("Monday", 1);
}
@Test
void test1_invertMapUsingForLoop() {
Map<Integer, String> inversedMap = InvertHashMapExample.invertMapUsingForLoop(sourceMap);
assertNotNull(inversedMap);
assertEquals(inversedMap.size(), 2);
assertEquals("Monday", inversedMap.get(1));
}
@Test
void test2_invertMapUsingStreams() {
Map<Integer, String> inversedMap = InvertHashMapExample.invertMapUsingStreams(sourceMap);
assertNotNull(inversedMap);
assertEquals(inversedMap.size(), 2);
assertEquals("Monday", inversedMap.get(1));
}
@Test
void test3_invertMapUsingMapper() {
Map<Integer, String> inversedMap = InvertHashMapExample.invertMapUsingMapper(sourceMap);
assertNotNull(inversedMap);
assertEquals(inversedMap.size(), 2);
assertEquals("Monday", inversedMap.get(1));
}
@Test
void test4_invertMapUsingGroupingBy() {
sourceMap.put("monday", 1);
Map<Integer, List<String>> inversedMap = InvertHashMapExample.invertMapUsingGroupingBy(sourceMap);
assertNotNull(inversedMap);
assertEquals(inversedMap.size(), 2);
assertTrue(inversedMap.get(1) instanceof List);
}
}