Nowadays software developments aim on managed code that organizes the memory occupation itself automatically by using the runtime environment. Hence, this is supposed to be very time intensive but simplifies the implementation in an immense way. Therefore, Java is used to determine the advantages and disadvantages of managed code in numerical simulations. In a first step a 3-D electrostatic FEM formulation is implemented in pure Java code by using an object-oriented structure based on design patterns. For an example of a 3-D numerical problem the processing time and the memory occupation are investigated and discussed regarding the use of pure Java code.