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BAEL-4719 - Using the Map.Entry Java Class (#10428) 

* BAEL-4719

Using the Map.Entry Java Class

* BAEL-4719

Using the Map.Entry Java Class

* BAEL-4719

Change description

* BAEL-4719

Feedback from first draft
This commit is contained in:
dvyshd 2021-01-28 23:53:49 +00:00 committed by GitHub
parent dd2ecbb9ee
commit d11f1163ab
4 changed files with 127 additions and 0 deletions
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35
java-collections-maps-3/src/main/java/com/baeldung/map/entry/Book.java Normal file
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package com.baeldung.map.entry;
public class Book {
private String title;
private String author;
public Book(String title, String author) {
this.title = title;
this.author = author;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
@Override
public String toString() {
return "Book{" +
"title='" + title + '\'' +
", author='" + author + '\'' +
'}';
}
}

34
java-collections-maps-3/src/main/java/com/baeldung/map/entry/MapEntryEfficiencyExample.java Normal file
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package com.baeldung.map.entry;
import java.util.HashMap;
import java.util.Map;
public class MapEntryEfficiencyExample {
public static void main(String[] args) {
MapEntryEfficiencyExample mapEntryEfficiencyExample = new MapEntryEfficiencyExample();
Map<String, String> map = new HashMap<>();
map.put("Robert C. Martin", "Clean Code");
map.put("Joshua Bloch", "Effective Java");
System.out.println("Iterating Using Map.KeySet - 2 operations");
mapEntryEfficiencyExample.usingKeySet(map);
System.out.println("Iterating Using Map.Entry - 1 operation");
mapEntryEfficiencyExample.usingEntrySet(map);
}
public void usingKeySet(Map<String, String> bookMap) {
for (String key : bookMap.keySet()) {
System.out.println("key: " + key + " value: " + bookMap.get(key));
}
}
public void usingEntrySet(Map<String, String> bookMap) {
for (Map.Entry<String, String> book: bookMap.entrySet()) {
System.out.println("key: " + book.getKey() + " value: " + book.getValue());
}
}
}

25
java-collections-maps-3/src/main/java/com/baeldung/map/entry/MapEntryTupleExample.java Normal file
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package com.baeldung.map.entry;
import java.util.*;
public class MapEntryTupleExample {
public static void main(String[] args) {
Map.Entry<String, Book> tuple1;
Map.Entry<String, Book> tuple2;
Map.Entry<String, Book> tuple3;
tuple1 = new AbstractMap.SimpleEntry<>("9780134685991", new Book("Effective Java 3d Edition", "Joshua Bloch"));
tuple2 = new AbstractMap.SimpleEntry<>("9780132350884", new Book("Clean Code", "Robert C Martin"));
tuple3 = new AbstractMap.SimpleEntry<>("9780132350884", new Book("Clean Code", "Robert C Martin"));
List<Map.Entry<String, Book>> orderedTuples = new ArrayList<>();
orderedTuples.add(tuple1);
orderedTuples.add(tuple2);
orderedTuples.add(tuple3);
for (Map.Entry<String, Book> tuple : orderedTuples) {
System.out.println("key: " + tuple.getKey() + " value: " + tuple.getValue());
}
}
}

33
java-collections-maps-3/src/test/java/com/baeldung/map/entry/MapEntryUnitTest.java Normal file
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package com.baeldung.map.entry;
import org.junit.Test;
import java.util.*;
import static org.junit.Assert.assertEquals;
public class MapEntryUnitTest {
@Test
public void givenSimpleEntryList_whenAddDuplicateKey_thenDoesNotOverwriteExistingKey() {
List<Map.Entry<String, Book>> orderedTuples = new ArrayList<>();
orderedTuples.add(new AbstractMap.SimpleEntry<>("9780134685991", new Book("Effective Java 3d Edition", "Joshua Bloch")));
orderedTuples.add(new AbstractMap.SimpleEntry<>("9780132350884", new Book("Clean Code", "Robert C Martin")));
orderedTuples.add(new AbstractMap.SimpleEntry<>("9780132350884", new Book("Clean Code", "Robert C Martin")));
assertEquals(3, orderedTuples.size());
assertEquals("9780134685991", orderedTuples.get(0).getKey());
assertEquals("9780132350884", orderedTuples.get(1).getKey());
assertEquals("9780132350884", orderedTuples.get(2).getKey());
}
@Test
public void givenRegularMap_whenAddDuplicateKey_thenOverwritesExistingKey() {
Map<String, Book> entries = new HashMap<>();
entries.put("9780134685991", new Book("Effective Java 3d Edition", "Joshua Bloch"));
entries.put("9780132350884", new Book("Clean Code", "Robert C Martin"));
entries.put("9780132350884", new Book("Clean Code", "Robert C Martin"));
assertEquals(2, entries.size());
}
}