Milestone 1: 1 — Project Scaffold, Core Email Parsing, and CLI Entry Point

emailslicer-dkasargod-java/.mvn/wrapper/maven-wrapper.properties

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+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.6/apache-maven-3.9.6-bin.zip
+wrapperUrl=https://repo.maven.apache.org/maven2/org/apache/maven/wrapper/maven-wrapper/3.2.0/maven-wrapper-3.2.0.jar

emailslicer-dkasargod-java/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>
+
+    <groupId>com.emailslicer</groupId>
+    <artifactId>email-slicer</artifactId>
+    <version>1.0.0</version>
+    <packaging>jar</packaging>
+
+    <name>Email Slicer</name>
+    <description>A CLI tool that parses an email address into its username and domain parts</description>
+
+    <properties>
+        <maven.compiler.source>17</maven.compiler.source>
+        <maven.compiler.target>17</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <junit.version>5.10.2</junit.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>email-slicer</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-jar-plugin</artifactId>
+                <version>3.3.0</version>
+                <configuration>
+                    <archive>
+                        <manifest>
+                            <mainClass>com.emailslicer.Main</mainClass>
+                        </manifest>
+                    </archive>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>3.2.5</version>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.12.1</version>
+                <configuration>
+                    <source>17</source>
+                    <target>17</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

emailslicer-dkasargod-java/src/main/java/com/emailslicer/EmailParts.java

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+package com.emailslicer;
+
+/**
+ * Immutable value object holding the parsed username and domain parts of an email address.
+ *
+ * @param username the local part of the email address (before the {@code @} symbol)
+ * @param domain   the domain part of the email address (after the {@code @} symbol)
+ */
+public record EmailParts(String username, String domain) {
+}

emailslicer-dkasargod-java/src/main/java/com/emailslicer/EmailSlicer.java

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+package com.emailslicer;
+
+/**
+ * Parses an email address string into its username and domain components.
+ *
+ * <p>This class contains the core parsing logic, separated from I/O concerns
+ * to allow direct unit testing without mocking {@code System.in}/{@code System.out}.
+ */
+public final class EmailSlicer {
+
+    private EmailSlicer() {
+        // Utility class — not instantiable
+    }
+
+    /**
+     * Parses the given email string into an {@link EmailParts} record.
+     *
+     * <p>The input is trimmed before validation. Validation requires:
+     * <ul>
+     *   <li>Input is not null or blank</li>
+     *   <li>Input contains exactly one {@code @} character</li>
+     *   <li>Both the username (before {@code @}) and domain (after {@code @}) are non-empty</li>
+     * </ul>
+     *
+     * @param email the raw email address string
+     * @return an {@link EmailParts} instance containing the username and domain
+     * @throws IllegalArgumentException if the input fails validation
+     */
+    public static EmailParts parse(String email) {
+        if (email == null || email.isBlank()) {
+            throw new IllegalArgumentException(Messages.INVALID_EMAIL_MESSAGE);
+        }
+
+        String trimmed = email.strip();
+
+        int atIndex = trimmed.indexOf('@');
+        if (atIndex == -1) {
+            throw new IllegalArgumentException(Messages.INVALID_EMAIL_MESSAGE);
+        }
+
+        // Reject multiple '@' characters
+        if (trimmed.indexOf('@', atIndex + 1) != -1) {
+            throw new IllegalArgumentException(Messages.INVALID_EMAIL_MESSAGE);
+        }
+
+        String username = trimmed.substring(0, atIndex);
+        String domain = trimmed.substring(atIndex + 1);
+
+        if (username.isEmpty() || domain.isEmpty()) {
+            throw new IllegalArgumentException(Messages.INVALID_EMAIL_MESSAGE);
+        }
+
+        return new EmailParts(username, domain);
+    }
+}

emailslicer-dkasargod-java/src/main/java/com/emailslicer/Main.java

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+package com.emailslicer;
+
+import java.util.Scanner;
+
+/**
+ * CLI entry point for the Email Slicer application.
+ *
+ * <p>Prompts the user for an email address, delegates parsing to
+ * {@link EmailSlicer#parse(String)}, and prints the result. Exits with
+ * code 1 when the input is invalid.
+ */
+public final class Main {
+
+    private Main() {
+        // Entry-point class — not instantiable
+    }
+
+    public static void main(String[] args) {
+        System.out.println(Messages.PROMPT_MESSAGE);
+
+        try (Scanner scanner = new Scanner(System.in)) {
+            String email = scanner.nextLine().strip();
+
+            try {
+                EmailParts parts = EmailSlicer.parse(email);
+                System.out.println(Messages.USERNAME_PREFIX + parts.username());
+                System.out.println(Messages.DOMAIN_PREFIX + parts.domain());
+            } catch (IllegalArgumentException e) {
+                System.out.println(e.getMessage());
+                System.exit(1);
+            }
+        }
+    }
+}

emailslicer-dkasargod-java/src/main/java/com/emailslicer/Messages.java

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+package com.emailslicer;
+
+/**
+ * Centralised store for user-facing messages.
+ */
+public final class Messages {
+
+    public static final String PROMPT_MESSAGE = "Please enter your Email Id:";
+    public static final String INVALID_EMAIL_MESSAGE = "Please enter a valid Email Id.";
+    public static final String USERNAME_PREFIX = "Your username is:  ";
+    public static final String DOMAIN_PREFIX = "Your domain is:  ";
+
+    private Messages() {
+        // Utility class — not instantiable
+    }
+}

emailslicer-dkasargod-java/src/test/java/com/emailslicer/EmailSlicerTest.java

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+package com.emailslicer;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Unit tests for {@link EmailSlicer#parse(String)}.
+ */
+class EmailSlicerTest {
+
+    @Test
+    @DisplayName("Valid email is split into username and domain")
+    void validEmail() {
+        EmailParts result = EmailSlicer.parse("avimax37@gmail.com");
+        assertEquals(new EmailParts("avimax37", "gmail.com"), result);
+    }
+
+    @Test
+    @DisplayName("Leading and trailing whitespace is trimmed before parsing")
+    void leadingTrailingWhitespace() {
+        EmailParts result = EmailSlicer.parse("  user@example.org  ");
+        assertEquals(new EmailParts("user", "example.org"), result);
+    }
+
+    @Test
+    @DisplayName("Missing '@' throws IllegalArgumentException")
+    void missingAtSign() {
+        IllegalArgumentException ex = assertThrows(
+                IllegalArgumentException.class,
+                () -> EmailSlicer.parse("invalidemail")
+        );
+        assertEquals(Messages.INVALID_EMAIL_MESSAGE, ex.getMessage());
+    }
+
+    @Test
+    @DisplayName("Empty string throws IllegalArgumentException")
+    void emptyString() {
+        assertThrows(IllegalArgumentException.class, () -> EmailSlicer.parse(""));
+    }
+
+    @Test
+    @DisplayName("Null input throws IllegalArgumentException")
+    void nullInput() {
+        assertThrows(IllegalArgumentException.class, () -> EmailSlicer.parse(null));
+    }
+
+    @Test
+    @DisplayName("Multiple '@' signs throws IllegalArgumentException")
+    void multipleAtSigns() {
+        assertThrows(IllegalArgumentException.class, () -> EmailSlicer.parse("a@b@c.com"));
+    }
+
+    @Test
+    @DisplayName("Empty username (@domain.com) throws IllegalArgumentException")
+    void emptyUsername() {
+        assertThrows(IllegalArgumentException.class, () -> EmailSlicer.parse("@domain.com"));
+    }
+
+    @Test
+    @DisplayName("Empty domain (user@) throws IllegalArgumentException")
+    void emptyDomain() {
+        assertThrows(IllegalArgumentException.class, () -> EmailSlicer.parse("user@"));
+    }
+}