code: @Override
      public void visitCode(Code obj) {
          unusedParms.clear();
          regToParm.clear();
          stack.resetForMethodEntry(this);
          Method m = getMethod();
          String methodName = m.getName();
          if (IGNORE_METHODS.contains(methodName)) {
              return;
          }
  
          int accessFlags = m.getAccessFlags();
          if (((accessFlags & (Const.ACC_STATIC | Const.ACC_PRIVATE)) == 0) || ((accessFlags & Const.ACC_SYNTHETIC) != 0)) {
              return;
          }
  
          List<String> parmTypes = SignatureUtils.getParameterSignatures(m.getSignature());
  
          if (parmTypes.isEmpty()) {
              return;
          }
          int firstReg = 0;
          if ((accessFlags & Const.ACC_STATIC) == 0) {
              ++firstReg;
          }
  
          int reg = firstReg;
          for (int i = 0; i < parmTypes.size(); ++i) {
              unusedParms.set(reg);
              regToParm.put(Integer.valueOf(reg), Integer.valueOf(i + 1));
              String parmSig = parmTypes.get(i);
              reg += SignatureUtils.getSignatureSize(parmSig);
          }
  
          try {
              super.visitCode(obj);
  
              if (!unusedParms.isEmpty()) {
                  LocalVariableTable lvt = m.getLocalVariableTable();
  
                  reg = unusedParms.nextSetBit(firstReg);
                  while (reg >= 0) {
                      LocalVariable lv = (lvt == null) ? null : lvt.getLocalVariable(reg, 0);
                      if (lv != null) {
                          String parmName = lv.getName();
                          bugReporter.reportBug(new BugInstance(this, BugType.UP_UNUSED_PARAMETER.name(), NORMAL_PRIORITY).addClass(this).addMethod(this)
                                  .addString("Parameter " + regToParm.get(Integer.valueOf(reg)) + ": " + parmName));
                      }
                      reg = unusedParms.nextSetBit(reg + 1);
                  }
              }
          } catch (StopOpcodeParsingException e) {
              // no unusedParms left
          }
      }
docs: implements the visitor to clear the parm set, and check for potential methods
  
  @param obj
  the context object of the currently parsed code block