Add java support

compiled_starters/java/.gitattributes

@@ -0,0 +1 @@
+* text=auto

compiled_starters/java/.gitignore

@@ -0,0 +1,4 @@
+java_grep.jar
+target/*
+target/
+.idea/

compiled_starters/java/README.md

@@ -0,0 +1,40 @@
+![progress-banner](https://codecrafters.io/landing/images/default_progress_banners/grep.png)
+
+This is a starting point for Java solutions to the
+["Build Your Own grep" Challenge](https://app.codecrafters.io/courses/grep/overview).
+
+[Regular expressions](https://en.wikipedia.org/wiki/Regular_expression)
+(Regexes, for short) are patterns used to match character combinations in
+strings. [`grep`](https://en.wikipedia.org/wiki/Grep) is a CLI tool for
+searching using Regexes.
+
+In this challenge you'll build your own implementation of `grep`. Along the way
+we'll learn about Regex syntax, how parsers/lexers work, and how regular
+expressions are evaluated.
+
+**Note**: If you're viewing this repo on GitHub, head over to
+[codecrafters.io](https://codecrafters.io) to try the challenge.
+
+# Passing the first stage
+
+The entry point for your `grep` implementation is in `src/main/java/Main.java`.
+Study and uncomment the relevant code, and push your changes to pass the first
+stage:
+
+```sh
+git add .
+git commit -m "pass 1st stage" # any msg
+git push origin master
+```
+
+Time to move on to the next stage!
+
+# Stage 2 & beyond
+
+Note: This section is for stages 2 and beyond.
+
+1. Ensure you have `java (21)` installed locally
+1. Run `./your_grep.sh` to run your program, which is implemented in
+   `src/main/java/Main.java`.
+1. Commit your changes and run `git push origin master` to submit your solution
+   to CodeCrafters. Test output will be streamed to your terminal.

compiled_starters/java/codecrafters.yml

@@ -0,0 +1,11 @@
+# Set this to true if you want debug logs.
+#
+# These can be VERY verbose, so we suggest turning them off
+# unless you really need them.
+debug: false
+
+# Use this to change the Java version used to run your code
+# on Codecrafters.
+#
+# Available versions: java-21
+language_pack: java-21

compiled_starters/java/pom.xml

@@ -0,0 +1,52 @@
+<?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>io.codecrafters</groupId>
+    <artifactId>build-your-own-grep</artifactId>
+    <version>1.0</version>
+
+    <properties>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <java.version>21</java.version>
+    </properties>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <configuration>
+                    <finalName>java_grep</finalName> <!-- Please do not change this final artifact name-->
+                    <descriptorRefs>
+                        <descriptorRef>jar-with-dependencies</descriptorRef>
+                    </descriptorRefs>
+                    <appendAssemblyId>false</appendAssemblyId>
+                    <archive>
+                        <manifest>
+                            <addClasspath>true</addClasspath>
+                            <!-- This is the main class of your program which will be executed-->
+                            <mainClass>Main</mainClass>
+                        </manifest>
+                    </archive>
+                    <outputDirectory>${dir}</outputDirectory>
+                </configuration>
+
+                <executions>
+                    <execution>
+                        <id>make-assembly</id>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>single</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

compiled_starters/java/src/main/java/Main.java

@@ -0,0 +1,24 @@
+import java.util.Scanner;
+
+public class Main {
+  public static void main(String[] args){
+    // You can use print statements as follows for debugging, they'll be visible when running tests.
+    System.out.println("Logs from your program will appear here!");
+
+    if(args.length < 2 || !args[0].equals("-E")) {
+      System.out.println("Expected first argument to be -E");
+      return;
+    }
+
+    final String pattern = args[1];
+    final Scanner input = new Scanner(System.in);
+    final String inputLine = input.nextLine();
+
+    // Uncomment this block to pass the first stage
+    // if (inputLine.contains(pattern)) {
+    //   System.exit(0);
+    // } else {
+    //   System.exit(1);
+    // }
+  }
+}

compiled_starters/java/your_grep.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+#
+# DON'T EDIT THIS!
+#
+# CodeCrafters uses this file to test your code. Don't make any changes here!
+#
+# DON'T EDIT THIS!
+set -e
+mvn -B --quiet package -Ddir=/tmp/codecrafters-grep-target
+exec java -jar /tmp/codecrafters-grep-target/java_grep.jar "$@"

course-definition.yml

@@ -28,6 +28,8 @@ languages:
     release_status: "alpha"
     alpha_tester_usernames: ["rohitpaulk", "sreeram-venkitesh"]
   - slug: "rust"
+  - slug: "java"
+    release_status: "beta"
 
 marketing:
   difficulty: medium

dockerfiles/java-21.Dockerfile

@@ -0,0 +1,16 @@
+FROM maven:3.9.5-eclipse-temurin-21-alpine
+
+COPY pom.xml /app/pom.xml
+
+WORKDIR /app
+
+# Download the dependencies
+RUN mvn -B package -Ddir=/tmp/codecrafters-grep-target
+
+# Cache Dependencies
+RUN mkdir -p /app-cached
+RUN mv /app/target /app-cached # Is this needed?
+
+# Pre-compile steps
+RUN echo "cd \${CODECRAFTERS_SUBMISSION_DIR} && mvn -B package -Ddir=/tmp/codecrafters-grep-target && sed -i 's/^\(mvn .*\)/#\1/' ./your_grep.sh" > /codecrafters-precompile.sh
+RUN chmod +x /codecrafters-precompile.sh

solutions/java/01-init/code/.gitattributes

@@ -0,0 +1 @@
+* text=auto

solutions/java/01-init/code/.gitignore

@@ -0,0 +1,4 @@
+java_grep.jar
+target/*
+target/
+.idea/

solutions/java/01-init/code/README.md

@@ -0,0 +1,40 @@
+![progress-banner](https://codecrafters.io/landing/images/default_progress_banners/grep.png)
+
+This is a starting point for Java solutions to the
+["Build Your Own grep" Challenge](https://app.codecrafters.io/courses/grep/overview).
+
+[Regular expressions](https://en.wikipedia.org/wiki/Regular_expression)
+(Regexes, for short) are patterns used to match character combinations in
+strings. [`grep`](https://en.wikipedia.org/wiki/Grep) is a CLI tool for
+searching using Regexes.
+
+In this challenge you'll build your own implementation of `grep`. Along the way
+we'll learn about Regex syntax, how parsers/lexers work, and how regular
+expressions are evaluated.
+
+**Note**: If you're viewing this repo on GitHub, head over to
+[codecrafters.io](https://codecrafters.io) to try the challenge.
+
+# Passing the first stage
+
+The entry point for your `grep` implementation is in `src/main/java/Main.java`.
+Study and uncomment the relevant code, and push your changes to pass the first
+stage:
+
+```sh
+git add .
+git commit -m "pass 1st stage" # any msg
+git push origin master
+```
+
+Time to move on to the next stage!
+
+# Stage 2 & beyond
+
+Note: This section is for stages 2 and beyond.
+
+1. Ensure you have `java (21)` installed locally
+1. Run `./your_grep.sh` to run your program, which is implemented in
+   `src/main/java/Main.java`.
+1. Commit your changes and run `git push origin master` to submit your solution
+   to CodeCrafters. Test output will be streamed to your terminal.

solutions/java/01-init/code/codecrafters.yml

@@ -0,0 +1,11 @@
+# Set this to true if you want debug logs.
+#
+# These can be VERY verbose, so we suggest turning them off
+# unless you really need them.
+debug: false
+
+# Use this to change the Java version used to run your code
+# on Codecrafters.
+#
+# Available versions: java-21
+language_pack: java-21

solutions/java/01-init/code/pom.xml

@@ -0,0 +1,52 @@
+<?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>io.codecrafters</groupId>
+    <artifactId>build-your-own-grep</artifactId>
+    <version>1.0</version>
+
+    <properties>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <java.version>21</java.version>
+    </properties>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <configuration>
+                    <finalName>java_grep</finalName> <!-- Please do not change this final artifact name-->
+                    <descriptorRefs>
+                        <descriptorRef>jar-with-dependencies</descriptorRef>
+                    </descriptorRefs>
+                    <appendAssemblyId>false</appendAssemblyId>
+                    <archive>
+                        <manifest>
+                            <addClasspath>true</addClasspath>
+                            <!-- This is the main class of your program which will be executed-->
+                            <mainClass>Main</mainClass>
+                        </manifest>
+                    </archive>
+                    <outputDirectory>${dir}</outputDirectory>
+                </configuration>
+
+                <executions>
+                    <execution>
+                        <id>make-assembly</id>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>single</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

solutions/java/01-init/code/src/main/java/Main.java

@@ -0,0 +1,20 @@
+import java.util.Scanner;
+
+public class Main {
+  public static void main(String[] args){
+    if(args.length < 2 || !args[0].equals("-E")) {
+      System.out.println("Expected first argument to be -E");
+      return;
+    }
+
+    final String pattern = args[1];
+    final Scanner input = new Scanner(System.in);
+    final String inputLine = input.nextLine();
+
+    if (inputLine.contains(pattern)) {
+      System.exit(0);
+    } else {
+      System.exit(1);
+    }
+  }
+}

solutions/java/01-init/code/your_grep.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+#
+# DON'T EDIT THIS!
+#
+# CodeCrafters uses this file to test your code. Don't make any changes here!
+#
+# DON'T EDIT THIS!
+set -e
+mvn -B --quiet package -Ddir=/tmp/codecrafters-grep-target
+exec java -jar /tmp/codecrafters-grep-target/java_grep.jar "$@"

solutions/java/01-init/diff/src/main/java/Main.java.diff

@@ -0,0 +1,30 @@
+@@ -1,24 +1,20 @@
+ import java.util.Scanner;
+
+ public class Main {
+   public static void main(String[] args){
+-    // You can use print statements as follows for debugging, they'll be visible when running tests.
+-    System.out.println("Logs from your program will appear here!");
+-
+     if(args.length < 2 || !args[0].equals("-E")) {
+       System.out.println("Expected first argument to be -E");
+       return;
+     }
+
+     final String pattern = args[1];
+     final Scanner input = new Scanner(System.in);
+     final String inputLine = input.nextLine();
+
+-    // Uncomment this block to pass the first stage
+-    // if (inputLine.contains(pattern)) {
+-    //   System.exit(0);
+-    // } else {
+-    //   System.exit(1);
+-    // }
++    if (inputLine.contains(pattern)) {
++      System.exit(0);
++    } else {
++      System.exit(1);
++    }
+   }
+ }

starter-repository-definitions.yml

@@ -137,3 +137,23 @@
   template_attributes:
     required_executable: "node (18)"
     user_editable_file: "app/main.js"
+
+- language: java
+  file_mappings:
+    - source: starter_templates/README.md
+      target: README.md
+    - source: starter_templates/codecrafters.yml
+      target: codecrafters.yml
+    - source: starter_templates/java/your_grep.sh
+      target: your_grep.sh
+    - source: starter_templates/java/.gitignore
+      target: .gitignore
+    - source: starter_templates/java/src/main/java/Main.java
+      target: src/main/java/Main.java
+    - source: starter_templates/java/pom.xml
+      target: pom.xml
+    - source: starter_templates/.gitattributes
+      target: .gitattributes
+  template_attributes:
+    required_executable: "java (21)"
+    user_editable_file: "src/main/java/Main.java"

starter_templates/codecrafters.yml

@@ -52,8 +52,8 @@ language_pack: elixir-1.10
 language_pack: kotlin-1.4
 {{/ language_is_kotlin }}
 {{# language_is_java }}
-# Available versions: java-1.8
-language_pack: java-1.8
+# Available versions: java-21
+language_pack: java-21
 {{/ language_is_java }}
 {{# language_is_nim }}
 # Available versions: nim-1.0

starter_templates/java/.gitignore

@@ -0,0 +1,4 @@
+java_grep.jar
+target/*
+target/
+.idea/