Add java support

compiled_starters/java/.gitattributes

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+* text=auto

compiled_starters/java/.gitignore

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+java_sqlite.jar
+target/*
+target/
+.idea/

compiled_starters/java/README.md

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+![progress-banner](https://codecrafters.io/landing/images/default_progress_banners/sqlite.png)
+
+This is a starting point for Java solutions to the
+["Build Your Own SQLite" Challenge](https://codecrafters.io/challenges/sqlite).
+
+In this challenge, you'll build a barebones SQLite implementation that supports
+basic SQL queries like `SELECT`. Along the way we'll learn about
+[SQLite's file format](https://www.sqlite.org/fileformat.html), how indexed data
+is
+[stored in B-trees](https://jvns.ca/blog/2014/10/02/how-does-sqlite-work-part-2-btrees/)
+and more.
+
+**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 SQLite 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_sqlite3.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.
+
+# Sample Databases
+
+To make it easy to test queries locally, we've added a sample database in the
+root of this repository: `sample.db`.
+
+This contains two tables: `apples` & `oranges`. You can use this to test your
+implementation for the first 6 stages.
+
+You can explore this database by running queries against it like this:
+
+```sh
+$ sqlite3 sample.db "select id, name from apples"
+1|Granny Smith
+2|Fuji
+3|Honeycrisp
+4|Golden Delicious
+```
+
+There are two other databases that you can use:
+
+1. `superheroes.db`:
+   - This is a small version of the test database used in the table-scan stage.
+   - It contains one table: `superheroes`.
+   - It is ~1MB in size.
+1. `companies.db`:
+   - This is a small version of the test database used in the index-scan stage.
+   - It contains one table: `companies`, and one index: `idx_companies_country`
+   - It is ~7MB in size.
+
+These aren't included in the repository because they're large in size. You can
+download them by running this script:
+
+```sh
+./download_sample_databases.sh
+```
+
+If the script doesn't work for some reason, you can download the databases
+directly from
+[codecrafters-io/sample-sqlite-databases](https://github.com/codecrafters-io/sample-sqlite-databases).

compiled_starters/java/codecrafters.yml

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+# 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/download_sample_databases.sh

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+#!/bin/sh
+
+echo "Downloading superheroes.db: ~1MB (used in stage 7)"
+curl -Lo superheroes.db https://raw.githubusercontent.com/codecrafters-io/sample-sqlite-databases/master/superheroes.db
+
+echo "Downloading companies.db: ~7MB (used in stage 8)"
+curl -Lo companies.db https://raw.githubusercontent.com/codecrafters-io/sample-sqlite-databases/master/companies.db
+
+echo "Sample databases downloaded."

compiled_starters/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>io.codecrafters</groupId>
+    <artifactId>build-your-own-sqlite</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_sqlite</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

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+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+public class Main {
+  public static void main(String[] args){
+    if (args.length < 2) {
+      System.out.println("Missing <database path> and <command>");
+      return;
+    }
+
+    String databaseFilePath = args[0];
+    String command = args[1];
+
+    switch (command) {
+      case ".dbinfo" -> {
+        try {
+          byte[] header = Files.readAllBytes(Path.of(databaseFilePath));
+
+          // The page size is stored at the 16th byte offset, using 2 bytes in big-endian order.
+          // '& 0xFFFF' is used to convert the signed short to an unsigned int.
+          int pageSize = ByteBuffer.wrap(header).order(ByteOrder.BIG_ENDIAN).position(16).getShort() & 0xFFFF;
+
+          // 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!");
+
+          // Uncomment this block to pass the first stage
+          // System.out.println("database page size: " + pageSize);
+        } catch (IOException e) {
+          System.out.println("Error reading file: " + e.getMessage());
+        }
+      }
+      default -> System.out.println("Missing or invalid command passed: " + command);
+    }
+  }
+}

compiled_starters/java/your_sqlite3.sh

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+#!/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-sqlite-target
+exec java -jar /tmp/codecrafters-sqlite-target/java_sqlite.jar "$@"

compiled_starters/javascript/app/main.js

@@ -9,7 +9,7 @@ if (command === ".dbinfo") {
   const { buffer } = await databaseFileHandler.read({
     length: 100,
     position: 0,
-    buffer: Buffer.alloc(100)
+    buffer: Buffer.alloc(100),
   });
 
   // You can use print statements as follows for debugging, they'll be visible when running tests.

course-definition.yml

@@ -28,6 +28,8 @@ languages:
     release_status: "alpha"
     alpha_tester_usernames: ["Terky"]
   - slug: "zig"
+  - slug: "java"
+    release_status: "beta"
 
 marketing:
   difficulty: hard

dockerfiles/java-21.Dockerfile

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+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-sqlite-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-sqlite-target && sed -i 's/^\(mvn .*\)/#\1/' ./your_sqlite3.sh" > /codecrafters-precompile.sh
+RUN chmod +x /codecrafters-precompile.sh

solutions/cpp/01-init/diff/src/Server.cpp.diff

@@ -24,12 +24,12 @@
 
 -        // Uncomment this to pass the first stage
 -        // database_file.seekg(16);  // Skip the first 16 bytes of the header
--        //
+-        // 
 -        // char buffer[2];
 -        // database_file.read(buffer, 2);
--        //
+-        // 
 -        // unsigned short page_size = (static_cast<unsigned char>(buffer[1]) | (static_cast<unsigned char>(buffer[0]) << 8));
--        //
+-        // 
 -        // std::cout << "database page size: " << page_size << std::endl;
 +        database_file.seekg(16);  // Skip the first 16 bytes of the header
 +

solutions/cpp/01-init/explanation.md

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+The entry point for your SQLite implementation is in `src/Server.cpp`.
+
+Study and uncomment the relevant code: 
+
+```cpp
+// Uncomment this to pass the first stage
+database_file.seekg(16);  // Skip the first 16 bytes of the header
+
+char buffer[2];
+database_file.read(buffer, 2);
+
+unsigned short page_size = (static_cast<unsigned char>(buffer[1]) | (static_cast<unsigned char>(buffer[0]) << 8));
+
+std::cout << "database page size: " << page_size << std::endl;
+```
+
+Push your changes to pass the first stage:
+
+```
+git add .
+git commit -m "pass 1st stage" # any msg
+git push origin master
+```

solutions/csharp/01-init/diff/src/Program.cs.diff

@@ -1,35 +1,35 @@
 @@ -1,29 +1,25 @@
- using static System.Buffers.Binary.BinaryPrimitives;
-
- // Parse arguments
- var (path, command) = args.Length switch
- {
-     0 => throw new InvalidOperationException("Missing <database path> and <command>"),
-     1 => throw new InvalidOperationException("Missing <command>"),
-     _ => (args[0], args[1])
- };
-
- var databaseFile = File.OpenRead(path);
-
- // Parse command and act accordingly
- if (command == ".dbinfo")
- {
--    // You can use print statements as follows for debugging, they'll be visible when running tests.
--    Console.WriteLine("Logs from your program will appear here!");
--
--    // Uncomment this line to pass the first stage
--    // databaseFile.Seek(16, SeekOrigin.Begin); // Skip the first 16 bytes
--    // byte[] pageSizeBytes = new byte[2];
--    // databaseFile.Read(pageSizeBytes, 0, 2);
--    // var pageSize = ReadUInt16BigEndian(pageSizeBytes);
--    // Console.WriteLine($"database page size: {pageSize}");
-+    databaseFile.Seek(16, SeekOrigin.Begin); // Skip the first 16 bytes
-+    byte[] pageSizeBytes = new byte[2];
-+    databaseFile.Read(pageSizeBytes, 0, 2);
-+    var pageSize = ReadUInt16BigEndian(pageSizeBytes);
-+    Console.WriteLine($"database page size: {pageSize}");
- }
- else
- {
-     throw new InvalidOperationException($"Invalid command: {command}");
- }
+ using static System.Buffers.Binary.BinaryPrimitives;
+ 
+ // Parse arguments
+ var (path, command) = args.Length switch
+ {
+     0 => throw new InvalidOperationException("Missing <database path> and <command>"),
+     1 => throw new InvalidOperationException("Missing <command>"),
+     _ => (args[0], args[1])
+ };
+ 
+ var databaseFile = File.OpenRead(path);
+ 
+ // Parse command and act accordingly
+ if (command == ".dbinfo")
+ {
+-    // You can use print statements as follows for debugging, they'll be visible when running tests.
+-    Console.WriteLine("Logs from your program will appear here!");
+-
+-    // Uncomment this line to pass the first stage
+-    // databaseFile.Seek(16, SeekOrigin.Begin); // Skip the first 16 bytes
+-    // byte[] pageSizeBytes = new byte[2];
+-    // databaseFile.Read(pageSizeBytes, 0, 2);
+-    // var pageSize = ReadUInt16BigEndian(pageSizeBytes);
+-    // Console.WriteLine($"database page size: {pageSize}");
++    databaseFile.Seek(16, SeekOrigin.Begin); // Skip the first 16 bytes
++    byte[] pageSizeBytes = new byte[2];
++    databaseFile.Read(pageSizeBytes, 0, 2);
++    var pageSize = ReadUInt16BigEndian(pageSizeBytes);
++    Console.WriteLine($"database page size: {pageSize}");
+ }
+ else
+ {
+     throw new InvalidOperationException($"Invalid command: {command}");
+ }

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

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+* text=auto

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

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+java_sqlite.jar
+target/*
+target/
+.idea/