Merge pull request #52 from urielsalis/java-support

Add java support

Author: rohitpaulk

compiled_starters/java/.gitattributes

@@ -0,0 +1 @@
+* 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/sample.db

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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/src/main/java/Main.java

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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/java/your_sqlite3.sh

@@ -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.