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BAEL-4719 - Using the Map.Entry Java Class (eugenp#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
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‎java-collections-maps-3/src/main/java/com/baeldung/map/entry/Book.java‎

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package com.baeldung.map.entry;
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public class Book {
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private String title;
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private String author;
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public Book(String title, String author) {
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this.title = title;
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this.author = author;
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}
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public String getTitle() {
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return title;
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}
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public void setTitle(String title) {
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this.title = title;
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}
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public String getAuthor() {
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return author;
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}
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public void setAuthor(String author) {
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this.author = author;
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}
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@Override
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public String toString() {
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return "Book{" +
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"title='" + title + '\'' +
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", author='" + author + '\'' +
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'}';
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}
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}

‎java-collections-maps-3/src/main/java/com/baeldung/map/entry/MapEntryEfficiencyExample.java‎

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

‎java-collections-maps-3/src/main/java/com/baeldung/map/entry/MapEntryTupleExample.java‎

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

‎java-collections-maps-3/src/test/java/com/baeldung/map/entry/MapEntryUnitTest.java‎

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

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