Moving the file to a different directory works. twisti@workstation:/$ cacao -jar javac.jar Exception in thread "main" java.lang.NoClassDefFoundError: com.sun.tools.javac.Main not found in java.lang.ClassLoader$1{urls=[file://javac.jar], parent=null} <<No stacktrace available>> Caused by: java.lang.ClassNotFoundException: com.sun.tools.javac.Main not found in java.lang.ClassLoader$1{urls=[file://javac.jar], parent=null} at java.net.URLClassLoader.findClass(URLClassLoader.java:530) at java.lang.ClassLoader.loadClass(ClassLoader.java:341) at java.lang.ClassLoader$1.loadClass(ClassLoader.java:1112) at java.lang.ClassLoader.loadClass(ClassLoader.java:293)