This buildfile is part of projectlombok.org. It is responsible for tasks that help with setting up the build infrastructure. None of these tasks are normally needed, unless modifying how the build works, such as updating dependencies. You need to specify the JDK9+ jdk whose jdk.compiler and java.compiler modules are to be converted. Use -Dtarget.jdk.ver=14 to automate this, or type a version in now (for example: 11): Aborted (no version entered) Using VM at: ${target.jdk} You need to specify the JDK9+ jdk whose jdk.compiler and java.compiler modules are to be converted. Run ant with -Dtarget.jdk=/full/path/here to automate this, or type the path in now (for example: /Library/JavaVirtualMachines/jdk-14.jdk/Contents/Home): This tool converts javac as stored in jmods of JDK distributions; JDK8 and below doesn't ship like that, and you don't need this for 8 and below. ${target.javac.version.full} <ivy-module version="2.0"> <info organisation="net.java.openjdk.custom" module="javac${target.javac.shortversion}" revision="${target.javac.version}" publication="${target.javac.pubstamp}"> <license name="GNU General Public License v2 with Classpath Exception" url="https://openjdk.java.net/legal/gplv2+ce.html" /> <description homepage="https://openjdk.java.net" /> </info> <configurations> <conf name="runtime" /> </configurations> <publications> <artifact name="javac${target.javac.shortversion}-java.compiler" conf="runtime" url="https://projectlombok.org/ivyrepo/langtools/javac${target.javac.version}-java.compiler.jar" /> <artifact name="javac${target.javac.shortversion}-jdk.compiler" conf="runtime" url="https://projectlombok.org/ivyrepo/langtools/javac${target.javac.version}-jdk.compiler.jar" /> </publications> </ivy-module> File build/javac${target.javac.version}-java.compiler.jar and build/javac${target.javac.version}-jdk.compiler.jar are available for upload; custom ivy target made as GAV net.java.openjdk.custom::javac${target.javac.shortversion}::${target.javac.version}