Initial commit: Java runtime code compilation prototype

Add Bazel-based Java project demonstrating runtime code compilation and
execution using the Java Compiler API.

Core features:
- CodeRunner API for compiling and executing Java code from strings
- RuntimeCompiler using javax.tools.JavaCompiler for in-memory compilation
- CLI interface with built-in examples and file-based code execution
- Support for BiFunction<U, D, T> interface with key/keyData parameters
- Access to Java standard library and Guava

Security considerations:
- Prominent warnings about lack of sandboxing
- Documentation clearly states prototype/educational use only
- Not suitable for production or untrusted input

Includes:
- 4 core implementation files
- 6 working examples (simple, math, list, guava, filter, map)
- 4 example code files users can run
- Comprehensive README and quick start guide

---
Prompt:
```
Create a bazel java project demonstrating the ability to take in code as a
string and compile and run it. The idea I have is that our code provides an API
* runCode(key: U, code: String) : T

We have a that takes in code and returns the output of running that code on the
data for that key.

The code contains a function in the interface `BiFunction<key: U, keyData: D,
output: T>`, and the system compiles the code and runs it. The function is
allowed to access the key value and key data, and it can use a known
allowlisted set of libraries like Guava or collections.

Make a prototype bazel project for this in a form that can shared publicly on
github with runnable examples (e.g., typing in code on the CLI or having code
in a local file).

For the purposes of the prototype, we'll ignore security. Add a clear warning
in any readmes we produce.
```

Author: dhalperi

.bazelrc

@@ -0,0 +1,2 @@
+# Enable WORKSPACE for Bazel 8
+common --enable_workspace

.gitignore

@@ -0,0 +1,27 @@
+# Bazel
+/bazel-*
+/.bazel-cache/
+
+# IDE
+/.idea/
+/.vscode/
+/.bsp/
+/.bazelbsp/
+*.iml
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Java
+*.class
+*.jar
+*.war
+*.ear
+hs_err_pid*
+
+# Logs
+*.log

BUILD.bazel

@@ -0,0 +1,21 @@
+load("@rules_java//java:defs.bzl", "java_binary", "java_library")
+
+java_library(
+    name = "code_runner",
+    srcs = glob(["src/main/java/com/example/coderunner/*.java"]),
+    visibility = ["//visibility:public"],
+    deps = [
+        "@maven//:com_google_guava_guava",
+        "@maven//:com_google_code_findbugs_jsr305",
+    ],
+)
+
+java_binary(
+    name = "cli",
+    srcs = ["src/main/java/com/example/coderunner/CLI.java"],
+    main_class = "com.example.coderunner.CLI",
+    deps = [
+        ":code_runner",
+        "@maven//:com_google_guava_guava",
+    ],
+)

QUICKSTART.md

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+# Quick Start Guide
+
+## ⚠️ Security Warning
+This tool executes arbitrary code without sandboxing. **For prototyping only!**
+
+## Run Your First Example
+
+1. **List available examples:**
+   ```bash
+   bazel run //:cli -- list
+   ```
+
+2. **Run a simple example:**
+   ```bash
+   bazel run //:cli -- example simple
+   ```
+
+3. **Try the Guava example:**
+   ```bash
+   bazel run //:cli -- example guava
+   ```
+
+## Run Code from a File
+
+1. **Create a simple Java file** (`MyCode.java`):
+   ```java
+   import java.util.function.BiFunction;
+
+   public class MyCode implements BiFunction<String, String, String> {
+       @Override
+       public String apply(String key, String data) {
+           return key + " processed: " + data;
+       }
+   }
+   ```
+
+2. **Run it:**
+   ```bash
+   bazel run //:cli -- file /path/to/MyCode.java mykey "test data"
+   ```
+
+## Use the API in Your Code
+
+```java
+import com.example.coderunner.CodeRunner;
+
+public class Example {
+    public static void main(String[] args) throws Exception {
+        CodeRunner<String, String, String> runner = new CodeRunner<>();
+
+        String code = """
+            import java.util.function.BiFunction;
+
+            public class MyFunction implements BiFunction<String, String, String> {
+                public String apply(String key, String data) {
+                    return key + ": " + data.toUpperCase();
+                }
+            }
+            """;
+
+        String result = runner.runCode("test", "hello world", code);
+        System.out.println(result);  // Prints: test: HELLO WORLD
+    }
+}
+```
+
+## Try the Examples
+
+All examples are in the `examples/` directory. Run them using absolute paths:
+
+```bash
+# Word counter
+bazel run //:cli -- file $PWD/examples/WordCounter.java doc "hello world test"
+
+# Calculator
+bazel run //:cli -- file $PWD/examples/Calculator.java add "10,20"
+
+# List processor (uses Guava)
+bazel run //:cli -- file $PWD/examples/ListProcessor.java items "a,b,c,d"
+```
+
+## What Can Your Code Do?
+
+Your code can use:
+- ✅ Java standard library
+- ✅ Guava library
+- ✅ Collections and Streams
+- ✅ Any Java language features
+- ⚠️ **BUT: No sandboxing! Full system access!**
+
+## Next Steps
+
+- Read the [full README](README.md) for details
+- Check the [examples directory](examples/) for more samples
+- Review [CodeRunner.java](src/main/java/com/example/coderunner/CodeRunner.java) for API details