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anuraggoyal1ashleyfrieze
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[BAEL-1951]create new module core-java-nio and adding java filechannel examples (eugenp#6899)
* create new module core-java-nio and adding filechannel * updated readme with NIO article details * fixed typo * Remore unused dependencies from pom.xml * fixed build issue * moving into core-java-modules folder * remove unused plugins from pom.xml * remove junk file and update readme * removing readme.md * change in indentation. remove tabs to spaces
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‎core-java-modules/core-java-nio/.gitignore‎

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0.*
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# Files generated by integration tests
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# *.txt
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/temp

‎core-java-modules/core-java-nio/pom.xml‎

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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<artifactId>core-java-nio</artifactId>
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<version>0.1.0-SNAPSHOT</version>
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<name>core-java-nio</name>
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<packaging>jar</packaging>
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<parent>
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<groupId>com.baeldung</groupId>
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<artifactId>parent-java</artifactId>
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<version>0.0.1-SNAPSHOT</version>
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<relativePath>../../parent-java</relativePath>
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</parent>
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</project>

‎core-java-modules/core-java-nio/src/test/java/com/baeldung/filechannel/FileChannelUnitTest.java‎

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package com.baeldung.filechannel;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertNotNull;
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import java.io.ByteArrayOutputStream;
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import java.io.FileInputStream;
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import java.io.FileOutputStream;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import java.nio.ByteBuffer;
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import java.nio.MappedByteBuffer;
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import java.nio.channels.FileChannel;
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import java.nio.channels.FileLock;
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import java.nio.charset.StandardCharsets;
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import org.junit.Test;
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public class FileChannelUnitTest {
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@Test
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public void givenFile_whenReadWithFileChannelUsingRandomAccessFile_thenCorrect() throws IOException {
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try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r");
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FileChannel channel = reader.getChannel();
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ByteArrayOutputStream out = new ByteArrayOutputStream()) {
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int bufferSize = 1024;
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if (bufferSize > channel.size()) {
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bufferSize = (int) channel.size();
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}
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ByteBuffer buff = ByteBuffer.allocate(bufferSize);
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while (channel.read(buff) > 0) {
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out.write(buff.array(), 0, buff.position());
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buff.clear();
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}
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String fileContent = new String(out.toByteArray(), StandardCharsets.UTF_8);
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assertEquals("Hello world", fileContent);
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}
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}
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@Test
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public void givenFile_whenReadWithFileChannelUsingFileInputStream_thenCorrect() throws IOException {
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try (ByteArrayOutputStream out = new ByteArrayOutputStream();
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FileInputStream fin = new FileInputStream("src/test/resources/test_read.in");
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FileChannel channel = fin.getChannel()) {
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int bufferSize = 1024;
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if (bufferSize > channel.size()) {
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bufferSize = (int) channel.size();
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}
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ByteBuffer buff = ByteBuffer.allocate(bufferSize);
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while (channel.read(buff) > 0) {
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out.write(buff.array(), 0, buff.position());
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buff.clear();
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}
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String fileContent = new String(out.toByteArray(), StandardCharsets.UTF_8);
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assertEquals("Hello world", fileContent);
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}
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}
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@Test
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public void givenFile_whenReadAFileSectionIntoMemoryWithFileChannel_thenCorrect() throws IOException {
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try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r");
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FileChannel channel = reader.getChannel();
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ByteArrayOutputStream out = new ByteArrayOutputStream()) {
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MappedByteBuffer buff = channel.map(FileChannel.MapMode.READ_ONLY, 6, 5);
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if (buff.hasRemaining()) {
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byte[] data = new byte[buff.remaining()];
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buff.get(data);
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assertEquals("world", new String(data, StandardCharsets.UTF_8));
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}
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}
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}
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@Test
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public void whenWriteWithFileChannelUsingRandomAccessFile_thenCorrect() throws IOException {
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String file = "src/test/resources/test_write_using_filechannel.txt";
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try (RandomAccessFile writer = new RandomAccessFile(file, "rw");
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FileChannel channel = writer.getChannel()) {
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ByteBuffer buff = ByteBuffer.wrap("Hello world".getBytes(StandardCharsets.UTF_8));
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channel.write(buff);
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// now we verify whether the file was written correctly
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RandomAccessFile reader = new RandomAccessFile(file, "r");
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assertEquals("Hello world", reader.readLine());
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reader.close();
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}
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}
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@Test
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public void givenFile_whenWriteAFileUsingLockAFileSectionWithFileChannel_thenCorrect() throws IOException {
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try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "rw");
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FileChannel channel = reader.getChannel();
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FileLock fileLock = channel.tryLock(6, 5, Boolean.FALSE);) {
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assertNotNull(fileLock);
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}
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}
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@Test
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public void givenFile_whenReadWithFileChannelGetPosition_thenCorrect() throws IOException {
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try (ByteArrayOutputStream out = new ByteArrayOutputStream();
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RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r");
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FileChannel channel = reader.getChannel()) {
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int bufferSize = 1024;
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if (bufferSize > channel.size()) {
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bufferSize = (int) channel.size();
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}
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ByteBuffer buff = ByteBuffer.allocate(bufferSize);
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while (channel.read(buff) > 0) {
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out.write(buff.array(), 0, buff.position());
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buff.clear();
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}
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// the original file is 11 bytes long, so that's where the position pointer should be
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assertEquals(11, channel.position());
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channel.position(4);
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assertEquals(4, channel.position());
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}
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}
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@Test
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public void whenGetFileSize_thenCorrect() throws IOException {
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try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r");
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FileChannel channel = reader.getChannel()) {
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// the original file is 11 bytes long, so that's where the position pointer should be
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assertEquals(11, channel.size());
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}
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}
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@Test
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public void whenTruncateFile_thenCorrect() throws IOException {
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String input = "this is a test input";
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FileOutputStream fout = new FileOutputStream("src/test/resources/test_truncate.txt");
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FileChannel channel = fout.getChannel();
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ByteBuffer buff = ByteBuffer.wrap(input.getBytes());
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channel.write(buff);
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buff.flip();
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channel = channel.truncate(5);
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assertEquals(5, channel.size());
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fout.close();
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channel.close();
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}
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}

‎core-java-modules/core-java-nio/src/test/resources/.gitignore‎

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*.class
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#folders#
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/target
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/neoDb*
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/data
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/src/main/webapp/WEB-INF/classes
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*/META-INF/*
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# Packaged files #
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*.jar
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*.war
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*.ear

‎core-java-modules/core-java-nio/src/test/resources/test_read.in‎

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Hello world

‎core-java-modules/core-java-nio/src/test/resources/test_truncate.txt‎

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this

‎core-java-modules/core-java-nio/src/test/resources/test_write_using_filechannel.txt‎

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Hello world

‎pom.xml‎

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<module>core-java-modules/core-java-concurrency-basic</module>
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<module>core-java-modules/core-java-concurrency-collections</module>
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<module>core-java-modules/core-java-io</module>
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<module>core-java-modules/core-java-nio</module>
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<module>core-java-modules/core-java-security</module>
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<module>core-java-modules/core-java-lang-syntax</module>
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<module>core-java-modules/core-java-lang</module>
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<module>core-java-modules/core-java-concurrency-basic</module>
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<module>core-java-modules/core-java-concurrency-collections</module>
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<module>core-java-modules/core-java-io</module>
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<module>core-java-modules/core-java-nio</module>
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<module>core-java-modules/core-java-security</module>
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<module>core-java-modules/core-java-lang-syntax</module>
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<module>core-java-modules/core-java-lang</module>
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<lombok.version>1.16.12</lombok.version>
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<h2.version>1.4.197</h2.version>
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</properties>
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</project>
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</project>

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