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BAEL-2800_Copying_a_HashMap_in_Java - generic types added

This commit is contained in:
Anshul Bansal 2019-04-08 11:08:20 +03:00
parent 68ffec2c2c
commit aae74f3b6c
2 changed files with 21 additions and 21 deletions
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35
core-java-collections-2/src/main/java/com/baeldung/copyinghashmap/CopyHashMap.java
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@ -2,6 +2,7 @@ package com.baeldung.copyinghashmap;
import java.util.HashMap; import java.util.HashMap;
import java.util.Map; import java.util.Map;
import java.util.Map.Entry;
import java.util.Set; import java.util.Set;
import java.util.stream.Collectors; import java.util.stream.Collectors;
@ -9,45 +10,45 @@ import org.apache.commons.lang3.SerializationUtils;
public class CopyHashMap { public class CopyHashMap {
public static HashMap copyUsingConstructor(HashMap originalMap) { public static <K, V> HashMap<K, V> copyUsingConstructor(HashMap<K, V> originalMap) {
return new HashMap(originalMap); return new HashMap<K, V>(originalMap);
} }
public static HashMap copyUsingClone(HashMap originalMap) { public static <K, V> HashMap<K, V> copyUsingClone(HashMap<K, V> originalMap) {
return (HashMap) originalMap.clone(); return (HashMap<K, V>) originalMap.clone();
} }
public static HashMap copyUsingPut(HashMap originalMap) { public static <K, V> HashMap<K, V> copyUsingPut(HashMap<K, V> originalMap) {
HashMap copyMap = new HashMap(); HashMap<K, V> copyMap = new HashMap<K, V>();
Set<Map.Entry> entries = originalMap.entrySet(); Set<Entry<K, V>> entries = originalMap.entrySet();
for(Map.Entry mapEntry: entries) { for(Map.Entry<K, V> mapEntry: entries) {
copyMap.put(mapEntry.getKey(), mapEntry.getValue()); copyMap.put((K)mapEntry.getKey(), (V)mapEntry.getValue());
} }
return copyMap; return copyMap;
} }
public static Map copyUsingPutAll(Map originalMap) { public static <K, V> HashMap<K, V> copyUsingPutAll(HashMap<K, V> originalMap) {
HashMap copyMap = new HashMap(); HashMap<K, V> copyMap = new HashMap<K, V>();
copyMap.putAll(originalMap); copyMap.putAll(originalMap);
return copyMap; return copyMap;
} }
public static HashMap copyUsingJava8Stream(HashMap originalMap) { public static <K, V> HashMap<K, V> copyUsingJava8Stream(HashMap<K, V> originalMap) {
Set<Map.Entry> entries = originalMap.entrySet(); Set<Entry<K, V>> entries = originalMap.entrySet();
HashMap copyMap = (HashMap) entries HashMap<K, V> copyMap = (HashMap<K, V>) entries
.stream() .stream()
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue)); .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
return copyMap; return copyMap;
} }
public static HashMap shallowCopy(HashMap originalMap) { public static <K, V> HashMap<K, V> shallowCopy(HashMap<K, V> originalMap) {
return (HashMap) originalMap.clone(); return (HashMap<K, V>) originalMap.clone();
} }
public static HashMap deepCopy(HashMap originalMap) { public static <K, V> HashMap<K, V> deepCopy(HashMap<K, V> originalMap) {
return SerializationUtils.clone(originalMap); return SerializationUtils.clone(originalMap);
} }

7
core-java-collections-2/src/test/java/com/baeldung/copyinghashmap/CopyHashMapUnitTest.java
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@ -1,6 +1,5 @@
package com.baeldung.copyinghashmap; package com.baeldung.copyinghashmap;
import static org.junit.Assert.assertEquals;
import static org.assertj.core.api.Assertions.assertThat; import static org.assertj.core.api.Assertions.assertThat;
import java.util.HashMap; import java.util.HashMap;
@ -21,7 +20,7 @@ public class CopyHashMapUnitTest {
map.put("emp1",emp1); map.put("emp1",emp1);
map.put("emp2",emp2); map.put("emp2",emp2);
HashMap shallowCopy = CopyHashMap.shallowCopy(map); HashMap<String, Employee> shallowCopy = CopyHashMap.shallowCopy(map);
assertThat(shallowCopy).isNotSameAs(map); assertThat(shallowCopy).isNotSameAs(map);
@ -36,7 +35,7 @@ public class CopyHashMapUnitTest {
map.put("emp1",emp1); map.put("emp1",emp1);
map.put("emp2",emp2); map.put("emp2",emp2);
HashMap shallowCopy = CopyHashMap.shallowCopy(map); HashMap<String, Employee> shallowCopy = CopyHashMap.shallowCopy(map);
emp1.setName("Johny"); emp1.setName("Johny");
@ -52,7 +51,7 @@ public class CopyHashMapUnitTest {
Employee emp2 = new Employee("Norman"); Employee emp2 = new Employee("Norman");
map.put("emp1",emp1); map.put("emp1",emp1);
map.put("emp2",emp2); map.put("emp2",emp2);
HashMap deepCopy = CopyHashMap.deepCopy(map); HashMap<String, Employee> deepCopy = CopyHashMap.deepCopy(map);
emp1.setName("Johny"); emp1.setName("Johny");