Compile java source from String without writing to file [duplicate]

Question

Here I have found some good example:

// Prepare source somehow.
String source = "package test; public class Test { static { System.out.println(\"hello\"); } public Test() { System.out.println(\"world\"); } }";

// Save source in .java file.
File root = new File("/java"); // On Windows running on C:\, this is C:\java.
File sourceFile = new File(root, "test/Test.java");
sourceFile.getParentFile().mkdirs();
new FileWriter(sourceFile).append(source).close();

// Compile source file.
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
compiler.run(null, null, null, sourceFile.getPath());

// Load and instantiate compiled class.
URLClassLoader classLoader = URLClassLoader.newInstance(new URL[] { root.toURI().toURL() });
Class<?> cls = Class.forName("test.Test", true, classLoader); // Should print "hello".
Object instance = cls.newInstance(); // Should print "world".
System.out.println(instance); // Should print "test.Test@hashcode".

Question: Is it possible to achieve exactly the same thing without writing to a file?

@Edit: To be more exact: I know how to compile from string (overloading JavaFileObject). But after doing this, I have no idea how to load the class. I probably missed the output-write part, but this also a thing I would like not to do.

@Edit2 For anyone interested, I created this small project to implement discussed feature: https://github.com/Krever/JIMCy

Answer 1

OK, so here is an example of using JavaCompiler to compile from a String input. this file is the core of it.

In this file, I load the class which is compiled. You will notice that I also detect the package and classname using regexes.

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As to the output, if you want to do that in memory, it appears that you can do so if you implement your own JavaFileManager; however I have never tried that!

Note that you can debug what happens quite easily by extending ForwardingJavaFileManager