Yep: Manifest-Version: 1.0 Ant-Version: Apache Ant 1.8.1 Created-By: 1.6.0_11-b03 (Sun Microsystems Inc.) Version: 4.0ea Main-Class: org.antlr.v4.Tool I think it's purely that javaw suppresses console output, and since ANTLR has no GUI it doesn't need javaw, and I should've been using java anyway.