How to Compile an RSPS Source in Java and Fix Classpath Errors (2026)

If you are trying to compile an RSPS source in Java and keep hitting classpath errors, you are not alone. RuneScape private server development is one of the most rewarding Java projects you can take on, but the compilation step trips up more beginners than anything else. In this guide, I will walk you through exactly how to compile your RSPS source and fix the classpath errors that block you from getting your server running.

Our team has spent years working with RSPS codebases, from old 317 revisions to modern 718+ servers, and we have seen every compilation error imaginable. The good news is that most of these problems share a handful of root causes that are easy to fix once you understand what the classpath does.

By the end of this article, you will know how to compile RSPS source files using both the command line and Eclipse IDE, configure your build path correctly, and troubleshoot the errors that pop up most often in 2026. Let us get your server running.

What Is a Classpath in Java and Why It Matters for RSPS?

The classpath is a parameter that tells the Java compiler (javac) and the Java Virtual Machine (JVM) where to look for user-defined classes and third-party libraries. Think of it as a search path. When your code says import org.rscd.Server, Java uses the classpath to track down where that Server class actually lives on your hard drive.

Without a correct classpath, Java cannot find the classes your code depends on. That is when you see errors like ClassNotFoundException or NoClassDefFoundError. For RSPS developers, this is the number one cause of compilation failures.

Compile-Time vs Runtime Classpath

There is an important distinction between the compile-time classpath and the runtime classpath that confuses many RSPS beginners. The compile-time classpath is used by javac to resolve imports and type references while it builds your .class files. The runtime classpath is used by the JVM when you actually run the server.

Your RSPS might compile successfully and still fail to launch if your runtime classpath is missing a JAR that the compiler had access to. This is why some users report that their RSPS compiles but does not run. Always verify both classpaths are configured correctly.

How Java Searches the Classpath

Java searches directories and JAR files in the order they appear in the classpath string, from left to right. On Windows, entries are separated by semicolons (;). On Linux and Mac, they are separated by colons (:). If two directories contain a class with the same name, Java picks the first one it finds.

This ordering matters for RSPS projects that ship multiple versions of the same library. If you have duplicate JARs in your lib folder, remove the older one to avoid unpredictable behavior.

Prerequisites for Compiling an RSPS Source

Before you can compile your RSPS source, you need the right tools installed on your system. Skipping any of these prerequisites is a guaranteed way to run into errors.

1. Install the Java Development Kit (JDK)

The JDK includes the javac compiler that turns your source files into bytecode. The Java Runtime Environment (JRE) is not enough because it lacks the compiler. Download and install the JDK from Oracle or use an open-source alternative like OpenJDK.

For most RSPS sources written in 2026, JDK 8 or JDK 11 works best. Some older 317 servers require JDK 8 specifically because they use APIs that were removed in newer Java versions. Check your source documentation for the recommended version.

2. Verify the JDK Is on Your System Path

After installing the JDK, open a terminal or command prompt and type javac -version. If you see a version number, you are good. If you see an error like “javac is not recognized as an internal or external command,” the JDK bin directory is not on your system PATH.

On Windows, add the JDK bin folder path to your system environment variables. On Linux and Mac, the JDK installer usually handles this automatically, but you may need to set JAVA_HOME manually.

3. Download Your RSPS Source and Dependencies

Make sure you have the complete RSPS source package. This typically includes the src folder (your Java source files), a lib or deps folder (external JAR files), and any data files the server needs. If any of these are missing, compilation will fail.

Extract the source to a folder path that does not contain spaces. A path like C:UsersJohn DoeMyServer can cause classpath errors because the space in the path confuses the Java compiler. Use something like C:RSPSMyServer instead.

Understanding the RSPS Project Structure

RSPS projects follow a fairly standard Java directory layout. Understanding this structure is critical because your classpath must point to the right folders. Here is what a typical RSPS project looks like.

Source Folder (src)

The src folder contains your .java files organized by package. For example, a 317 RSPS might have packages like com.rs2.model, com.rs2.net, and com.rs2.world. Each package corresponds to a subdirectory inside src.

When you compile, the package declaration at the top of each Java file must match the folder structure. If a file says package com.rs2.model but lives in src/com/rs2/net/, you will get a compilation error. This is one of the most common mistakes RSPS beginners make.

Library Folder (lib or deps)

The lib or deps folder holds all external JAR files your RSPS depends on. Common RSPS libraries include database drivers, networking libraries like Netty, and logging frameworks. Every JAR in this folder must be on your classpath during compilation.

Missing even one JAR from this folder will cause ClassNotFoundException errors. Always check that you have all the libraries the source author listed in the documentation.

Output Folder (bin or build)

After compilation, the resulting .class files are placed in an output folder, typically called bin or build. This is also the folder you need on your runtime classpath when launching the server. Eclipse creates this folder automatically, but if you are compiling from the command line, you need to specify it yourself.

How to Compile an RSPS Source in Java: Step-by-Step Guide

Now let us walk through the actual compilation process. I will use command-line instructions so you understand what happens under the hood, then cover Eclipse in the next section.

Step 1: Open Your Terminal and Navigate to the Project Root

Open a command prompt or terminal and use cd to navigate to your RSPS project root directory. This is the folder that contains your src and lib folders.

On Windows: cd C:RSPSMyServer

On Linux and Mac: cd /home/user/RSPS/MyServer

Step 2: Set Up Your Classpath Variable

Before compiling, set your classpath to include all JAR files in your lib folder. On Windows, you can use a wildcard to include all JARs at once.

On Windows: set CLASSPATH=.;lib*

On Linux and Mac: export CLASSPATH=.:lib/*

The dot (.) at the beginning adds the current directory to the classpath. The lib* or lib/* part tells Java to include every JAR file inside the lib folder. This is much easier than listing each JAR individually.

Step 3: Compile All Source Files

Now run the Java compiler with the -d flag to specify where compiled classes should go.

On Windows: javac -d bin -cp "lib*" srccomrs2*.java srccomrs2***.java

On Linux and Mac: javac -d bin -cp "lib/*" src/com/rs2/*.java

The -d bin flag sends compiled .class files to the bin folder. The -cp "lib/*" flag sets the classpath to include all libraries. If the compilation succeeds without errors, your bin folder will now contain the compiled bytecode.

Step 4: Run Your RSPS Server

To launch your compiled server, switch to the output directory and run the main class.

On Windows: java -cp "bin;lib*" com.rs2.Server

On Linux and Mac: java -cp "bin:lib/*" com.rs2.Server

Replace com.rs2.Server with the actual main class for your specific RSPS revision. If everything is configured correctly, your server will start up and begin listening for client connections.

Step 5: Verify the Server Is Running

After starting the server, open your RSPS client and connect to localhost on the default port (usually 43594). If the client connects successfully, your compilation was correct. If you get connection errors, check your firewall settings and make sure the port specified in your server configuration matches what the client expects.

Configuring Eclipse IDE for RSPS Build Path

Many RSPS developers prefer Eclipse because it handles compilation automatically and provides visual tools for managing the classpath. Here is how to set up Eclipse for an RSPS project.

Import the RSPS Project into Eclipse

Go to File > Import > General > Existing Projects into Workspace. Select your RSPS project folder and click Finish. Eclipse will import the project and attempt to build it automatically.

If you see red error markers immediately, do not panic. This usually means the build path is not configured yet.

Configure the Java Build Path

Right-click your project in the Package Explorer and select Properties > Java Build Path. This is where you control what Eclipse considers to be your classpath.

First, check the Source tab. Your src folder should be listed and marked as a source folder. If it is not, click Add Folder and select it. The output folder at the bottom should point to bin or your chosen build directory.

Next, switch to the Libraries tab. Here is where you add all external JAR files. Click Add JARs to select JARs from your project’s lib folder, or click Add External JARs if the libraries are outside your project.

Add All Dependencies

Select every JAR file in your lib folder and add it to the build path. Missing even one library will cause red error markers on your source files. After adding all JARs, click Apply and Close.

Eclipse will rebuild the project automatically. If the error markers disappear, your build path is correct. If any remain, the error messages will tell you exactly which class or package is missing so you can track down the right library.

Set the Correct JRE

In the Libraries tab, verify that a JRE System Library is listed and matches the Java version your RSPS requires. If you see a red X on the JRE entry, it means Eclipse cannot find the installed JDK. Click Edit and select the correct JDK from the list.

For older RSPS sources, you may need to add JDK 8 as an alternate JRE. Install it separately and point Eclipse to it in Window > Preferences > Java > Installed JREs.

Setting Up the .bat File for Windows RSPS Compilation

Many RSPS distributions include batch files for compiling and running the server on Windows. These .bat files automate the classpath setup so you do not have to type long commands every time.

Anatomy of a Compile Batch File

A typical RSPS compile batch file looks something like this.

@echo off

cd /d "%~dp0"

set CLASSPATH=.;lib*

javac -d bin -cp "lib*" srccomrs2*.java

pause

The cd /d "%~dp0" line changes the working directory to the folder where the batch file lives, regardless of where you run it from. This prevents path-related classpath errors. The pause at the end keeps the window open so you can read any error messages.

Common Batch File Problems

If your batch file fails, check for these issues. First, make sure the JDK is installed and on your PATH. Second, verify the lib folder path matches what the batch file expects. Third, remove any spaces from your folder path since the Java compiler can misinterpret them.

If you are running an old RSPS batch file written for a different source revision, the package paths in the javac command may not match your source structure. Update the package paths to match your actual src directory layout.

Creating a Run Batch File

You also need a batch file to run the compiled server. Here is a basic template.

@echo off

cd /d "%~dp0"

java -cp "bin;lib*" com.rs2.Server

pause

Make sure the main class name matches your actual server entry point. The runtime classpath here uses a semicolon to separate bin and lib* on Windows.

Compiling RSPS on Linux and Mac from the Command Line

Linux and Mac users often struggle because most RSPS tutorials assume Windows. The compilation process is actually simpler on Unix-like systems, but there are a few differences to account for.

Path Separators and Wildcards

On Linux and Mac, the classpath separator is a colon (:) instead of a semicolon. This is the most common mistake Windows-to-Linux converts make. A classpath that works on Windows as "bin;lib/*" must become "bin:lib/*" on Linux.

The forward slash (/) is the path delimiter on Unix systems. Use it consistently in all your paths.

Setting CLASSPATH Permanently

If you do not want to set the classpath every time you open a terminal, add it to your shell profile. Edit ~/.bashrc or ~/.zshrc and add a line like export CLASSPATH=.:lib/*.

Then run source ~/.bashrc to apply the change immediately. Now your classpath is set every time you open a terminal in your RSPS project directory.

Handling File Permissions

After downloading an RSPS source on Linux, the compile script may not have execute permissions. Run chmod +x compile.sh to make it executable. If no script is included, use the javac command directly as described in the step-by-step section above.

Common RSPS Classpath Errors and How to Fix Them

Now let us tackle the errors you are most likely to encounter. I have matched each error message to its root cause and provided the exact fix.

Error 1: ClassNotFoundException

This error means the JVM tried to load a class at runtime but could not find it on the classpath. The error message tells you the exact class name that is missing. For example, java.lang.ClassNotFoundException: org.mindrot.jbcrypt.BCrypt means the jBCrypt JAR is not on your classpath.

Fix: Find the JAR file that contains the missing class and add it to your classpath. If you are not sure which JAR contains it, search online for the class name plus “JAR download.” Add the JAR to your lib folder and rebuild.

Error 2: NoClassDefFoundError

This is similar to ClassNotFoundException but more subtle. It means a class was available at compile time but not at runtime. You will see this when your compile-time classpath has a JAR that your runtime classpath is missing.

Fix: Compare your compile and runtime classpaths. Make sure every JAR in the compile classpath is also in the runtime classpath. The most common cause is a missing entry in your run batch file or run configuration.

Error 3: “package does not exist” or “package java.lang does not exist”

This error typically means the JDK itself is not configured correctly. If you see “package java.lang does not exist,” the compiler cannot find the core Java libraries, which means the JDK is not properly installed or your JAVA_HOME variable points to the wrong location.

Fix: Reinstall the JDK and verify JAVA_HOME points to the JDK root directory, not the JRE. In Eclipse, go to Installed JREs and make sure a JDK (not just a JRE) is selected.

Error 4: “Could not find or load main class”

This error occurs when Java cannot find the main class you specified. It usually means your runtime classpath does not include the output folder containing your compiled classes.

Fix: Make sure the bin directory is on your runtime classpath. Double-check the main class name for typos. The full package path must be correct, including all subpackages.

Error 5: Directory Paths with Spaces

If your project lives in a path with spaces, like C:UsersJohn DoeRSPS, Java may fail to parse the classpath correctly. This is a frequent issue reported across RSPS forums.

Fix: Move your project to a path without spaces, such as C:RSPSMyServer. Always quote your classpath arguments in batch files to handle spaces if they cannot be avoided.

Error 6: Outdated Java Version Conflicts

Many older RSPS sources were written for Java 7 or 8 and use APIs that were deprecated or removed in newer versions. If you compile with JDK 17 or newer, you may see errors about removed APIs or internal sun classes.

Fix: Install the Java version recommended by your RSPS source documentation. For most legacy servers, that is JDK 8. You can run multiple JDK versions side by side and switch between them as needed.

RSPS Compilation FAQ

Final Thoughts on Compiling Your RSPS Source

Compiling an RSPS source in Java does not have to be a frustrating experience. Once you understand how the classpath works and why Java uses it to locate classes and libraries, most errors become straightforward to diagnose and fix. The key is setting up your classpath correctly from the start, using a clean folder path without spaces, and making sure every dependency is available at both compile time and runtime.

Start with the command-line approach so you understand what is happening behind the scenes. Then move to Eclipse for day-to-day development once you are comfortable. If you hit an error, match the exact error message to the solutions in this guide. Nine times out of ten, the fix is adding a missing JAR or correcting a path separator.

Your next step is to compile your source, launch the server, and connect with your client. Once you have a running server, you can start customizing content, adding features, and building the RuneScape private server you have been dreaming about. Happy developing.