code: protected InputStream getClassInputStream(String classInternalName) {
          if (classInternalName == null || "".equals(classInternalName)) {
              return null;
          }
  
          InputStream inputStream = null;
          try {
              for (File jarFile : jarFiles) {
                  ZipFile zipFile = new ZipFile(jarFile);
                  ZipEntry zipEntry = zipFile.getEntry(classInternalName + ".class");
                  if (zipEntry != null) {
                      InputStream zis = zipFile.getInputStream(zipEntry);
                      byte[] bytecode = toByteArray(zis);
                      if (isStreamForClass(new ByteArrayInputStream(bytecode), classInternalName)) {
                          inputStream = new ByteArrayInputStream(bytecode);
                      }
                      zis.close();
                  }
                  zipFile.close();
  
                  if (inputStream != null) {
                      return inputStream;
                  }
              }
  
              String fileName = classInternalName + ".class";
              fileName = fileName.substring(fileName.lastIndexOf('/') + 1);
              for (File classFile : classFiles) {
                  if (classFile.getName().equals(fileName)) {
                      FileInputStream fis = new FileInputStream(classFile);
                      byte[] bytecode = toByteArray(fis);
                      if (isStreamForClass(new ByteArrayInputStream(bytecode), classInternalName)) {
                          inputStream = new ByteArrayInputStream(bytecode);
                      }
                      fis.close();
                  }
                  if (inputStream != null) {
                      return inputStream;
                  }
              }
          } catch (IOException ioe) {
              ioe.printStackTrace();
          }
          return null;
      }
docs: Get an InputStream containing the byte code for the specified class.
  
  @param classInternalName the internal name of the class to find
  
  @return the input stream containing the class or null if the class is
  not part of the file set