Java - lesson 7 | HackIndia Skills

Key point

One build command

A good repo is not just source code. It has a build tool so another builder can clone it and run one clear command.

Use Maven or Gradle. For this track, Maven is the simpler default because many Java examples and college labs already use it.

What Maven does

Maven reads a file named pom.xml. That file tells Maven your Java version, dependencies, and how to compile the app.

You do not need to install every library by hand. If your project uses a JSON library, Maven downloads it from its central repository during the build.

Example

Small Maven file

Put this pom.xml in the root of your project. Update the groupId, artifactId, and mainClass for your app.

This example uses Java 17 and creates a runnable CLI jar with dependencies included.

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>in.hackindia</groupId>
    <artifactId>recruiter-cli</artifactId>
    <version>1.0.0</version>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.17.2</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.6.0</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <transformers>
                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>in.hackindia.recruiter.Main</mainClass>
                                </transformer>
                            </transformers>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Your to-do

Standard layout

Do each one yourself, then tap it to tick it off. The ticks are only a checklist for you: they are not marked or scored.

Create src/main/java for Java files.
Place your main class under a package, like in.hackindia.recruiter.
Keep sample JSON or CSV data in a data folder at the repo root.
Keep pom.xml at the repo root, not inside src.
Commit generated target files only if you have a reason. Usually add target/ to .gitignore.

0 of 5 done

Example

Build and run

From the project root, run these commands. This is what another builder should be able to do after cloning your repo.

mvn clean package
java -jar target/recruiter-cli-1.0.0.jar data/candidates.json

Common mistake

Common build mistake

Do not write instructions that only work in your IDE. HackIndia reviewers and other builders may use VS Code, IntelliJ, Eclipse, or only the terminal.

Your project should build from a fresh clone. If it needs a manual library download or a local absolute path like C:\Users\name\file.json, fix that.

Tip

Use AI carefully

You can ask ChatGPT, Gemini, or Claude to draft a pom.xml. Paste your package name, main class, Java version, and dependencies.

Check the result. Make sure the mainClass is real, the dependency versions exist, and the commands work on your machine before you commit.