code: public DoubleConstant addDouble(double value)
    {
      DoubleConstant entry = getDoubleByValue(value);
  
      if (entry != null)
        return entry;
  
      entry = new DoubleConstant(this, _entries.size(), value);
  
      addConstant(entry);
      addConstant(null);
  
      return entry;
    }
docs: Adds a double constant.