During generating a javap report For JDK 25 I get:
Error in parsing javap file:
java.lang.NullPointerException: Cannot invoke "String.equals(Object)" because "methodName" is null
at com.sun.tdk.jcov.report.javap.JavapClass.parseMethodString(JavapClass.java:204)
at com.sun.tdk.jcov.report.javap.JavapClass.parseJavapFile(JavapClass.java:109)
at com.sun.tdk.jcov.report.javap.JavapRepGen.run(JavapRepGen.java:152)
at com.sun.tdk.jcov.RepGen.run(RepGen.java:652)
at com.sun.tdk.jcov.tools.JCovCMDTool.run(JCovCMDTool.java:164)
at com.sun.tdk.jcov.RepGen.main(RepGen.java:363)


I have narrowed it down to a single class, attached.

My command line:
java -cp jcov.jar com.sun.tdk.jcov.RepGen -javap one_class one_class.xml

Use the attached class file (which you need to put into one_class/classes/sun/net/NetworkClient.class ) and an attached xml file.