Add stage 2 solutions for go, java and rust

solutions/go/02-rg2/code/.codecrafters/compile.sh

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+#!/bin/sh
+#
+# This script is used to compile your program on CodeCrafters
+#
+# This runs before .codecrafters/run.sh
+#
+# Learn more: https://codecrafters.io/program-interface
+
+set -e # Exit on failure
+
+go build -o /tmp/codecrafters-build-redis-go app/*.go

solutions/go/02-rg2/code/.codecrafters/run.sh

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+#!/bin/sh
+#
+# This script is used to run your program on CodeCrafters
+#
+# This runs after .codecrafters/compile.sh
+#
+# Learn more: https://codecrafters.io/program-interface
+
+set -e # Exit on failure
+
+exec /tmp/codecrafters-build-redis-go "$@"

solutions/go/02-rg2/code/.gitattributes

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+* text=auto

solutions/go/02-rg2/code/README.md

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+![progress-banner](https://codecrafters.io/landing/images/default_progress_banners/redis.png)
+
+This is a starting point for Go solutions to the
+["Build Your Own Redis" Challenge](https://codecrafters.io/challenges/redis).
+
+In this challenge, you'll build a toy Redis clone that's capable of handling
+basic commands like `PING`, `SET` and `GET`. Along the way we'll learn about
+event loops, the Redis protocol 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 Redis implementation is in `app/server.go`. Study and
+uncomment the relevant code, and push your changes to pass the first stage:
+
+```sh
+git commit -am "pass 1st stage" # any msg
+git push origin master
+```
+
+That's all!
+
+# Stage 2 & beyond
+
+Note: This section is for stages 2 and beyond.
+
+1. Ensure you have `go (1.19)` installed locally
+1. Run `./your_program.sh` to run your Redis server, which is implemented in
+   `app/server.go`.
+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/go/02-rg2/code/app/server.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+)
+
+func main() {
+	l, err := net.Listen("tcp", "0.0.0.0:6379")
+	if err != nil {
+		fmt.Println("Failed to bind to port 6379")
+		os.Exit(1)
+	}
+	conn, err := l.Accept()
+	if err != nil {
+		fmt.Println("Error accepting connection: ", err.Error())
+		os.Exit(1)
+	}
+	conn.Write([]byte("+PONG\r\n"))
+}

solutions/go/02-rg2/code/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 Go version used to run your code
+# on Codecrafters.
+#
+# Available versions: go-1.22
+language_pack: go-1.22

solutions/go/02-rg2/code/go.mod

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+// DON'T EDIT THIS!
+//
+// Codecrafters relies on this file being intact to run tests successfully. Any changes
+// here will not reflect when CodeCrafters tests your code, and might even cause build
+// failures.
+//
+// DON'T EDIT THIS!
+
+module github.com/codecrafters-io/redis-starter-go
+
+go 1.22

solutions/go/02-rg2/code/your_program.sh

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+#!/bin/sh
+#
+# Use this script to run your program LOCALLY.
+#
+# Note: Changing this script WILL NOT affect how CodeCrafters runs your program.
+#
+# Learn more: https://codecrafters.io/program-interface
+
+set -e # Exit early if any commands fail
+
+# Copied from .codecrafters/compile.sh
+#
+# - Edit this to change how your program compiles locally
+# - Edit .codecrafters/compile.sh to change how your program compiles remotely
+(
+  cd "$(dirname "$0")" # Ensure compile steps are run within the repository directory
+  go build -o /tmp/codecrafters-build-redis-go app/*.go
+)
+
+# Copied from .codecrafters/run.sh
+#
+# - Edit this to change how your program runs locally
+# - Edit .codecrafters/run.sh to change how your program runs remotely
+exec /tmp/codecrafters-build-redis-go "$@"

solutions/go/02-rg2/diff/app/server.go.diff

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+@@ -1,24 +1,21 @@
+ package main
+
+ import (
+ 	"fmt"
+ 	"net"
+ 	"os"
+ )
+
+-// Ensures gofmt doesn't remove the "net" and "os" imports in stage 1 (feel free to remove this!)
+-var _ = net.Listen
+-var _ = os.Exit
+-
+ func main() {
+ 	l, err := net.Listen("tcp", "0.0.0.0:6379")
+ 	if err != nil {
+ 		fmt.Println("Failed to bind to port 6379")
+ 		os.Exit(1)
+ 	}
+-	_, err = l.Accept()
++	conn, err := l.Accept()
+ 	if err != nil {
+ 		fmt.Println("Error accepting connection: ", err.Error())
+ 		os.Exit(1)
+ 	}
++	conn.Write([]byte("+PONG\r\n"))
+ }

solutions/go/02-rg2/explanation.md

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+The entry point for your Redis implementation is in `app/server.go`.
+
+Study and uncomment the relevant code: 
+
+```go
+// Uncomment this block to pass the first stage
+
+l, err := net.Listen("tcp", "0.0.0.0:6379")
+if err != nil {
+	fmt.Println("Failed to bind to port 6379")
+	os.Exit(1)
+}
+_, err = l.Accept()
+if err != nil {
+	fmt.Println("Error accepting connection: ", err.Error())
+	os.Exit(1)
+}
+```
+
+Push your changes to pass the first stage:
+
+```
+git add .
+git commit -m "pass 1st stage" # any msg
+git push origin master
+```

solutions/java/02-rg2/code/.codecrafters/compile.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+#
+# This script is used to compile your program on CodeCrafters
+#
+# This runs before .codecrafters/run.sh
+#
+# Learn more: https://codecrafters.io/program-interface
+
+set -e # Exit on failure
+
+mvn -B package -Ddir=/tmp/codecrafters-build-redis-java

solutions/java/02-rg2/code/.codecrafters/run.sh

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+#!/bin/sh
+#
+# This script is used to run your program on CodeCrafters
+#
+# This runs after .codecrafters/compile.sh
+#
+# Learn more: https://codecrafters.io/program-interface
+
+set -e # Exit on failure
+
+exec java -jar /tmp/codecrafters-build-redis-java/codecrafters-redis.jar "$@"

solutions/java/02-rg2/code/.gitattributes

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+* text=auto

solutions/java/02-rg2/code/.gitignore

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+*.jar
+target/
+.idea/

solutions/java/02-rg2/code/README.md

@@ -0,0 +1,34 @@
+![progress-banner](https://codecrafters.io/landing/images/default_progress_banners/redis.png)
+
+This is a starting point for Java solutions to the
+["Build Your Own Redis" Challenge](https://codecrafters.io/challenges/redis).
+
+In this challenge, you'll build a toy Redis clone that's capable of handling
+basic commands like `PING`, `SET` and `GET`. Along the way we'll learn about
+event loops, the Redis protocol 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 Redis 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 commit -am "pass 1st stage" # any msg
+git push origin master
+```
+
+That's all!
+
+# Stage 2 & beyond
+
+Note: This section is for stages 2 and beyond.
+
+1. Ensure you have `mvn` installed locally
+1. Run `./your_program.sh` to run your Redis server, 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/02-rg2/code/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-23
+language_pack: java-23

solutions/java/02-rg2/code/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>codecrafters-redis</artifactId>
+    <version>1.0</version>
+
+    <properties>
+        <maven.compiler.source>23</maven.compiler.source>
+        <maven.compiler.target>23</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <java.version>23</java.version>
+    </properties>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <configuration>
+                    <finalName>codecrafters-redis</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/02-rg2/code/src/main/java/Main.java

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+import java.io.IOException;
+import java.io.OutputStream;
+import java.net.ServerSocket;
+import java.net.Socket;
+
+public class Main {
+  public static void main(String[] args){
+       ServerSocket serverSocket = null;
+       Socket clientSocket = null;
+       int port = 6379;
+       try {
+         serverSocket = new ServerSocket(port);
+         // Since the tester restarts your program quite often, setting SO_REUSEADDR
+         // ensures that we don't run into 'Address already in use' errors
+         serverSocket.setReuseAddress(true);
+         // Wait for connection from client.
+         clientSocket = serverSocket.accept();
+         OutputStream outputStream = clientSocket.getOutputStream();
+         outputStream.write("+PONG\r\n".getBytes());
+       } catch (IOException e) {
+         System.out.println("IOException: " + e.getMessage());
+       } finally {
+         try {
+           if (clientSocket != null) {
+             clientSocket.close();
+           }
+         } catch (IOException e) {
+           System.out.println("IOException: " + e.getMessage());
+         }
+       }
+  }
+}

solutions/java/02-rg2/code/your_program.sh

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+#!/bin/sh
+#
+# Use this script to run your program LOCALLY.
+#
+# Note: Changing this script WILL NOT affect how CodeCrafters runs your program.
+#
+# Learn more: https://codecrafters.io/program-interface
+
+set -e # Exit early if any commands fail
+
+# Copied from .codecrafters/compile.sh
+#
+# - Edit this to change how your program compiles locally
+# - Edit .codecrafters/compile.sh to change how your program compiles remotely
+(
+  cd "$(dirname "$0")" # Ensure compile steps are run within the repository directory
+  mvn -B package -Ddir=/tmp/codecrafters-build-redis-java
+)
+
+# Copied from .codecrafters/run.sh
+#
+# - Edit this to change how your program runs locally
+# - Edit .codecrafters/run.sh to change how your program runs remotely
+exec java -jar /tmp/codecrafters-build-redis-java/codecrafters-redis.jar "$@"