diff --git a/core-java-modules/core-java-collections-maps-7/README.md b/core-java-modules/core-java-collections-maps-7/README.md
index 2e1531050e..a62bdda7af 100644
--- a/core-java-modules/core-java-collections-maps-7/README.md
+++ b/core-java-modules/core-java-collections-maps-7/README.md
@@ -1,5 +1,7 @@
-## Relevant Articles
+## Relevant Articles:
- [Difference Between putIfAbsent() and computeIfAbsent() in Java’s Map](https://www.baeldung.com/java-map-putifabsent-computeifabsent)
+- [How to Write and Read a File with a Java HashMap](https://www.baeldung.com/how-to-write-and-read-a-file-with-a-java-hashmap/)
- [How to Write Hashmap to CSV File](https://www.baeldung.com/java-write-hashmap-csv)
- [How to Get First or Last Entry From a LinkedHashMap in Java](https://www.baeldung.com/java-linkedhashmap-first-last-key-value-pair)
- [How to Write and Read a File with a Java HashMap](https://www.baeldung.com/java-hashmap-write-read-file)
+- More articles: [[<-- prev]](/core-java-modules/core-java-collections-maps-6)
\ No newline at end of file
diff --git a/core-java-modules/core-java-collections-maps-7/pom.xml b/core-java-modules/core-java-collections-maps-7/pom.xml
index cefee201cc..a7acded9cf 100644
--- a/core-java-modules/core-java-collections-maps-7/pom.xml
+++ b/core-java-modules/core-java-collections-maps-7/pom.xml
@@ -1,11 +1,15 @@
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
4.0.0
core-java-collections-maps-7
core-java-collections-maps-7
jar
+
+ 2.10.1
+ 1.5
+
core-java-modules
@@ -13,72 +17,24 @@
0.0.1-SNAPSHOT
-
- 5.2.5.RELEASE
-
com.fasterxml.jackson.core
jackson-databind
- 2.12.4
-
-
- org.openjdk.jmh
- jmh-core
- 1.36
+ ${jackson.version}
com.google.code.gson
gson
- 2.8.9
-
-
- org.json
- json
- 20230227
-
-
- junit
- junit
- 4.13.1
- test
-
-
- org.junit.jupiter
- junit-jupiter
- 5.8.1
- test
-
-
- org.junit.jupiter
- junit-jupiter
- 5.8.1
- test
-
-
- junit
- junit
- 4.13.1
- test
-
-
- org.junit.jupiter
- junit-jupiter
- 5.8.1
- test
-
-
- junit
- junit
- 4.13.1
- test
+ ${gson.version}
org.apache.commons
commons-csv
- 1.5
+ ${csv.version}
+
@@ -92,5 +48,4 @@
-
diff --git a/core-java-modules/core-java-collections-maps-7/src/main/java/com/baeldung/map/readandwritefile/Student.java b/core-java-modules/core-java-collections-maps-7/src/main/java/com/baeldung/map/readandwritefile/Student.java
new file mode 100644
index 0000000000..b981de6300
--- /dev/null
+++ b/core-java-modules/core-java-collections-maps-7/src/main/java/com/baeldung/map/readandwritefile/Student.java
@@ -0,0 +1,51 @@
+package com.baeldung.map.readandwritefile;
+
+import java.io.Serializable;
+import java.util.Objects;
+
+public class Student implements Serializable {
+ private static final long serialVersionUID = 1L;
+ private String firstName;
+ private String lastName;
+
+ /** Default constructor for JSON serialization */
+ public Student() {
+
+ }
+
+ public Student(String firstName, String lastName) {
+ this.firstName = firstName;
+ this.lastName = lastName;
+ }
+
+ public void setFirstName(String firstName) {
+ this.firstName = firstName;
+ }
+
+ public void setLastName(String lastName) {
+ this.lastName = lastName;
+ }
+
+ public String getFirstName() {
+ return firstName;
+ }
+
+ public String getLastName() {
+ return lastName;
+ }
+
+ @Override
+ public boolean equals(Object o) {
+ if (this == o)
+ return true;
+ if (o == null || getClass() != o.getClass())
+ return false;
+ Student student = (Student) o;
+ return Objects.equals(firstName, student.firstName) && Objects.equals(lastName, student.lastName);
+ }
+
+ @Override
+ public int hashCode() {
+ return super.hashCode();
+ }
+}
diff --git a/core-java-modules/core-java-collections-maps-7/src/test/java/com/baeldung/map/readandwritefile/ReadAndWriteFileWithHashMapUnitTest.java b/core-java-modules/core-java-collections-maps-7/src/test/java/com/baeldung/map/readandwritefile/ReadAndWriteFileWithHashMapUnitTest.java
new file mode 100644
index 0000000000..56867d3885
--- /dev/null
+++ b/core-java-modules/core-java-collections-maps-7/src/test/java/com/baeldung/map/readandwritefile/ReadAndWriteFileWithHashMapUnitTest.java
@@ -0,0 +1,135 @@
+package com.baeldung.map.readandwritefile;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.FileReader;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.OutputStream;
+import java.lang.reflect.Type;
+import java.nio.file.Files;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+import java.util.stream.Collectors;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.gson.Gson;
+import com.google.gson.reflect.TypeToken;
+
+import org.junit.After;
+import org.junit.Test;
+import org.junit.Before;
+
+public class ReadAndWriteFileWithHashMapUnitTest {
+
+ private static final Map STUDENT_DATA = new HashMap<>();
+
+ static {
+ STUDENT_DATA.put(1234, new Student("Henry", "Winter"));
+ STUDENT_DATA.put(5678, new Student("Richard", "Papen"));
+ }
+
+ private File file;
+
+ @Before
+ public void createFile() throws IOException {
+ file = File.createTempFile("student", ".data");
+ }
+
+ @After
+ public void deleteFile() {
+ file.delete();
+ }
+
+ @Test
+ public void givenHashMap_whenWrittenAsPropertiesFile_thenReloadedMapIsIdentical() throws IOException {
+ // Given a map containing student data
+ Map studentData = new HashMap<>();
+ studentData.put("student.firstName", "Henry");
+ studentData.put("student.lastName", "Winter");
+
+ // When converting to a Properties object and writing to a file
+ Properties props = new Properties();
+ props.putAll(studentData);
+ try (OutputStream output = Files.newOutputStream(file.toPath())) {
+ props.store(output, null);
+ }
+
+ // Then the map resulting from loading the Properties file is identical
+ Properties propsFromFile = new Properties();
+ try (InputStream input = Files.newInputStream(file.toPath())) {
+ propsFromFile.load(input);
+ }
+
+ Map studentDataFromProps = propsFromFile.stringPropertyNames()
+ .stream()
+ .collect(Collectors.toMap(key -> key, props::getProperty));
+ assertThat(studentDataFromProps).isEqualTo(studentData);
+ }
+
+ @Test
+ public void givenHashMap_whenSerializedToFile_thenDeserializedMapIsIdentical() throws IOException, ClassNotFoundException {
+ // Given a map containing student data (STUDENT_DATA)
+
+ // When serializing the map to a file
+ try (FileOutputStream fileOutput = new FileOutputStream(file); ObjectOutputStream objectStream = new ObjectOutputStream(fileOutput)) {
+ objectStream.writeObject(STUDENT_DATA);
+ }
+
+ // Then read the file back into a map and check the contents
+ Map studentsFromFile;
+ try (FileInputStream fileReader = new FileInputStream(file); ObjectInputStream objectStream = new ObjectInputStream(fileReader)) {
+ studentsFromFile = (HashMap) objectStream.readObject();
+ }
+ assertThat(studentsFromFile).isEqualTo(STUDENT_DATA);
+ }
+
+ @Test
+ public void givenHashMap_whenSerializedToFileWithJackson_thenDeserializedMapIsIdentical() throws IOException {
+ // Given a map containing student data (STUDENT_DATA)
+
+ // When converting to JSON with Jackson and writing to a file
+ ObjectMapper mapper = new ObjectMapper();
+ try (FileOutputStream fileOutput = new FileOutputStream(file)) {
+ mapper.writeValue(fileOutput, STUDENT_DATA);
+ }
+
+ // Then deserialize the file back into a map and check that it's identical
+ Map mapFromFile;
+ try (FileInputStream fileInput = new FileInputStream(file)) {
+ // Create a TypeReference so we can deserialize the parameterized type
+ TypeReference> mapType = new TypeReference>() {
+ };
+ mapFromFile = mapper.readValue(fileInput, mapType);
+ }
+ assertThat(mapFromFile).isEqualTo(STUDENT_DATA);
+ }
+
+ @Test
+ public void givenHashMap_whenSerializedToFileWithGson_thenDeserializedMapIsIdentical() throws IOException {
+ // Given a map containing student data (STUDENT_DATA)
+
+ // When converting to JSON using Gson and writing to a file
+ Gson gson = new Gson();
+ try (FileWriter writer = new FileWriter(file)) {
+ gson.toJson(STUDENT_DATA, writer);
+ }
+
+ // Then deserialize the file back into a map and check that it's identical
+ Map studentsFromFile;
+ try (FileReader reader = new FileReader(file)) {
+ Type mapType = new TypeToken>() {
+ }.getType();
+ studentsFromFile = gson.fromJson(reader, mapType);
+ }
+ assertThat(studentsFromFile).isEqualTo(STUDENT_DATA);
+ }
+}