code: @Override
      public void visitClassContext(ClassContext classContext) {
          try {
              ignoreRegs = new BitSet();
              tryBlocks = new BitSet();
              catchHandlers = new BitSet();
              switchTargets = new BitSet();
              monitorSyncPCs = new ArrayList<>(5);
              stack = new OpcodeStack();
              super.visitClassContext(classContext);
          } finally {
              ignoreRegs = null;
              tryBlocks = null;
              catchHandlers = null;
              switchTargets = null;
              monitorSyncPCs = null;
              stack = null;
          }
      }
docs: implements the visitor to create and the clear the register to location map
  
  @param classContext
  the context object of the currently parsed class