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BAEL-9283 Replacing specific words in a file in Java #18551

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Merged
merged 3 commits into from
May 30, 2025
Merged

BAEL-9283 Replacing specific words in a file in Java #18551

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802eda1
BAEL-9283 Replacing specific words in a file in Java & new java-io mo…
Tirth007 May 16, 2025
7eb63b8
Merge branch 'eugenp:master' into master
Tirth007 May 21, 2025
7514eed
BAEL-9283 try with resource & independent line separator usage
Tirth007 May 21, 2025
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37 changes: 37 additions & 0 deletions core-java-modules/core-java-io-8/pom.xml
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
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">
<modelVersion>4.0.0</modelVersion>
<artifactId>core-java-io-8</artifactId>
<packaging>jar</packaging>
<name>core-java-io-8</name>

<parent>
<groupId>com.baeldung.core-java-modules</groupId>
<artifactId>core-java-modules</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>

<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>${maven-compiler-plugin.version}</version>
<configuration>
<source>${java.version}</source>
<target>${java.version}</target>
<annotationProcessorPaths>
<path>
<groupId>org.openjdk.jmh</groupId>
<artifactId>jmh-generator-annprocess</artifactId>
<version>${jmh-generator.version}</version>
</path>
</annotationProcessorPaths>
</configuration>
</plugin>
</plugins>
</build>

</project>
100 changes: 100 additions & 0 deletions ...ore-java-io-8/src/test/java/com/baeldung/replacewordinfile/ReplaceWordInFileUnitTest.java
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package com.baeldung.replacewordinfile;

import static org.junit.jupiter.api.Assertions.assertEquals;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import org.apache.commons.io.FileUtils;
import org.junit.jupiter.api.Test;

public class ReplaceWordInFileUnitTest {

private static final String FILE_PATH = "src/test/resources/data.txt";
private static final String FILE_OUTPUT_PATH = "src/test/resources/data_output.txt";
private static final String OUTPUT_TO_VERIFY = "This is a test file."+System.lineSeparator()+"This is a test file."+System.lineSeparator()+"This is a test file.";

@Test
public void givenFile_whenUsingBufferedReader_thenReplacedWordCorrect() throws IOException {
StringBuilder fileContent = new StringBuilder();
try (BufferedReader br = Files.newBufferedReader(Paths.get(FILE_PATH))) {
String line;
while ((line = br.readLine()) != null){
fileContent.append(line).append(System.lineSeparator());
}
String replacedContent = fileContent.toString().replace("sample","test").trim();
try (FileWriter fw = new FileWriter(FILE_OUTPUT_PATH)) {
fw.write(replacedContent);
}

assertEquals(OUTPUT_TO_VERIFY,replacedContent);
}
}

@Test
public void givenFile_whenUsingScanner_thenReplacedWordCorrect() throws IOException {
StringBuilder fileContent = new StringBuilder();
try (Scanner scanner = new Scanner(new File(FILE_PATH))) {
while (scanner.hasNextLine()){
fileContent.append(scanner.nextLine()).append(System.lineSeparator());
}
String replacedContent = fileContent.toString().replace("sample","test").trim();
try (FileWriter fw = new FileWriter(FILE_OUTPUT_PATH)) {
fw.write(replacedContent);
}

assertEquals(OUTPUT_TO_VERIFY,replacedContent);
}
}

@Test
public void givenFile_whenUsingFilesAPI_thenReplacedWordCorrect() throws IOException{
try (Stream<String> lines = Files.lines(Paths.get(FILE_PATH))) {
List<String> list = lines.map(line -> line.replace("sample", "test"))
.collect(Collectors.toList());
Files.write(Paths.get(FILE_OUTPUT_PATH), list, StandardCharsets.UTF_8);

assertEquals(OUTPUT_TO_VERIFY,String.join(System.lineSeparator(), list));
}
}

@Test
public void givenFile_whenUsingFileUtils_thenReplacedWordCorrect() throws IOException{
StringBuilder fileContent = new StringBuilder();
List<String> lines = FileUtils.readLines(new File(FILE_PATH), "UTF-8");
lines.forEach(line -> fileContent.append(line).append(System.lineSeparator()));
String replacedContent = fileContent.toString().replace("sample","test").trim();
try (FileWriter fw = new FileWriter(FILE_OUTPUT_PATH)) {
fw.write(replacedContent);
}

assertEquals(OUTPUT_TO_VERIFY,replacedContent);
}

@Test
public void givenLargeFile_whenUsingFilesAPI_thenReplacedWordCorrect() throws IOException{
try (Stream<String> lines = Files.lines(Paths.get(FILE_PATH))) {
Files.writeString(Paths.get(FILE_OUTPUT_PATH), "",StandardCharsets.UTF_8, StandardOpenOption.CREATE,StandardOpenOption.TRUNCATE_EXISTING);
lines.forEach(line -> {
line = line.replace("sample", "test") + System.lineSeparator();
try {
Files.writeString(Paths.get(FILE_OUTPUT_PATH),line,StandardCharsets.UTF_8, StandardOpenOption.APPEND);
} catch (IOException e) {
throw new RuntimeException(e);
}
});

assertEquals(OUTPUT_TO_VERIFY,Files.readString(Paths.get(FILE_OUTPUT_PATH)).trim());
}
}
}
3 changes: 3 additions & 0 deletions core-java-modules/core-java-io-8/src/test/resources/data.txt
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This is a sample file.
This is a sample file.
This is a sample file.
3 changes: 3 additions & 0 deletions core-java-modules/core-java-io-8/src/test/resources/data_output.txt
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This is a test file.
This is a test file.
This is a test file.
1 change: 1 addition & 0 deletions core-java-modules/pom.xml
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Expand Up @@ -146,6 +146,7 @@
<module>core-java-io-4</module>
<module>core-java-io-5</module>
<module>core-java-io-7</module>
<module>core-java-io-8</module>
<!-- <module>core-java-io-6</module> --> <!-- failing after upgrade to jdk21 -->
<module>core-java-io-apis</module>
<module>core-java-io-apis-2</module>
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