add main class

build.gradle

@@ -1,11 +1,13 @@
 plugins {
     id 'java'
+    id 'application'
     id 'antlr'
 }
 
 group 'de.churl'
 version '1.0-SNAPSHOT'
 sourceCompatibility = '14'
+mainClassName = 'StupsCompiler'
 
 generateGrammarSource {
     outputDirectory = file("src/main/java/lexer")

src/main/java/StupsCompiler.java

@@ -0,0 +1,6 @@
+public class StupsCompiler {
+
+    public static void main(String[] args) {
+        System.out.println("StupsCompiler");
+    }
+}