Java — How to dynamically compile and load external java classes | Code Factory

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package com.example.java.programming;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import javax.tools.Diagnostic;
import javax.tools.DiagnosticCollector;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
public class InlineCompiler {
	public static void main(String[] args) {
		StringBuilder sb = new StringBuilder(64);
		sb.append("package com.example.java.programming;\n");
		sb.append("public class HelloWorld implements com.example.java.programming.InlineCompiler.DoStuff {\n");
		sb.append("    public void doStuff() {\n");
		sb.append("        System.out.println(\"Hello world\");\n");
		sb.append("    }\n");
		sb.append("}\n");
		File helloWorldJava = new File("src/main/java/com/example/java/programming/HelloWorld.java");
		if (helloWorldJava.getParentFile().exists() || helloWorldJava.getParentFile().mkdirs()) {
			try {
				Writer writer = null;
				try {
					writer = new FileWriter(helloWorldJava);
					writer.write(sb.toString());
					writer.flush();
				} finally {
					try {
						writer.close();
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
				/**
				 * Start - Compilation Requirements
				 **/
				DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
				JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
				StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, null);
				// This sets up the class path that the compiler will use.
				// I've added the .jar file that contains the DoStuff interface within in it...
				List<String> optionList = new ArrayList<String>();
				optionList.add("-classpath");
				optionList.add(System.getProperty("java.class.path") + File.pathSeparator + "dist/InlineCompiler.jar");
				
				Iterable<? extends JavaFileObject> compilationUnit = fileManager.getJavaFileObjectsFromFiles(Arrays.asList(helloWorldJava));
				JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, diagnostics, optionList, null, compilationUnit);
				/**
				 * End - Compilation Requirements
				 **/
				
				/*
				 * If you don't want to Execute/Run class file then return task.call()
				 * task.call() Returns : true if and only all the files compiled without errors;false otherwise
				 */ 
				if (task.call()) {
					/**
					 * Start - Load and execute
					 **/
					System.out.println("Yeah");
					// Create a new custom class loader, pointing to the directory that contains the
					// compiled classes, this should point to the top of the package structure!
					URLClassLoader classLoader = new URLClassLoader(new URL[] { new File("./").toURI().toURL() });
					// Load the class from the classloader by name....
					Class<?> loadedClass = classLoader.loadClass("com.example.java.programming.HelloWorld");
					// Create a new instance...
					Object obj = loadedClass.newInstance();
					// Santity check
					if (obj instanceof DoStuff) {
						// Cast to the DoStuff interface
						DoStuff stuffToDo = (DoStuff) obj;
						// Run it
						stuffToDo.doStuff();
					}
					/**
					 * End - Load and execute
					 **/
				} else {
					for (Diagnostic<? extends JavaFileObject> diagnostic : diagnostics.getDiagnostics()) {
						System.out.format("Error on line %d in %s%n", diagnostic.getLineNumber(), diagnostic.getSource().toUri());
					}
				}
				fileManager.close();
			} catch (IOException | ClassNotFoundException | InstantiationException | IllegalAccessException exp) {
				exp.printStackTrace();
			}
		}
	}
	public static interface DoStuff {
		public void doStuff();
	}
}

Output :

Yeah
Hello world