Compile code fully in memory with javax.tools.JavaCompiler [duplicate]

I’ve run the above code in Mac OS Java 7. None of them works. So i wrote one
https://github.com/trung/InMemoryJavaCompiler

StringBuilder source = new StringBuilder()
    .append("package org.mdkt;\n")
    .append("public class HelloClass {\n")
    .append("   public String hello() { return \"hello\"; }")
    .append("}");

Class<?> helloClass = InMemoryJavaCompiler.compile("org.mdkt.HelloClass", source.toString());