code: @Override
      public void sawOpcode(int seen) {
          try {
              stack.precomputation(this);
  
              if ((seen != Const.INVOKEVIRTUAL) || !"wait".equals(getNameConstantOperand()) || stack.getStackDepth() == 0) {
                  return;
              }
              JavaClass cls = stack.getStackItem(0).getJavaClass();
              if (cls != null) {
                  String clsName = cls.getClassName();
                  if (concurrentAwaitClasses.contains(clsName)) {
                      bugReporter.reportBug(new BugInstance(this, BugType.SWCO_SUSPICIOUS_WAIT_ON_CONCURRENT_OBJECT.name(), NORMAL_PRIORITY).addClass(this)
                              .addMethod(this).addSourceLine(this));
                  }
              }
          } catch (ClassNotFoundException cnfe) {
              bugReporter.reportMissingClass(cnfe);
          } finally {
              stack.sawOpcode(this, seen);
          }
      }
docs: implements the visitor to look for calls to wait, on java.util.concurrent classes that define await.
  
  @param seen
  the opcode of the currently visited instruction