CreateHappyNewYear.java

import java.io.IOException;
import javassist.CannotCompileException;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;
import javassist.CtNewMethod;

public class CreateHappyNewYear {

    public static void main(String[] args) throws IOException, CannotCompileException {
        ClassPool classPool = ClassPool.getDefault();
        CtClass happyNewYearClazz = classPool.makeClass("HappyNewYear");
        CtMethod method = CtNewMethod.make("public static void main(String[] args){"+ 
                                             "System.out.println(\"Happy New Year!\");" +
                                           "}", happyNewYearClazz);
        happyNewYearClazz.addMethod(method);
        happyNewYearClazz.writeFile(".");
    }
}