code: public boolean isPossibleExBuilder(int excReg) throws ClassNotFoundException {
          String sig = getSigConstantOperand();
          String returnSig = SignatureUtils.getReturnSignature(sig);
          if (returnSig.startsWith(Values.SIG_QUALIFIED_CLASS_PREFIX)) {
              returnSig = SignatureUtils.trimSignature(returnSig);
              JavaClass retCls = Repository.lookupClass(returnSig);
              if (retCls.instanceOf(throwableClass)) {
                  int numParms = SignatureUtils.getNumParameters(sig);
                  if (stack.getStackDepth() >= numParms) {
                      for (int p = 0; p < numParms; p++) {
                          OpcodeStack.Item item = stack.getStackItem(p);
                          if (item.getRegisterNumber() == excReg) {
                              return true;
                          }
                      }
                  }
              }
          }
          return false;
      }
docs: returns whether the method called might be a method that builds an exception using the original exception. It does so by looking to see if the method
  returns an exception, and if one of the parameters is the original exception
  
  @param excReg
  the register of the original exception caught
  @return whether this method call could be an exception builder method
  
  @throws ClassNotFoundException
  if the class of the return type can't be found