1. A computer implemented method for virtually executing a program having property declarations of classes in a first programming language that is a dynamic scripting language on an execution system of a second programming language, the method comprising the steps of: generating an interface class that is uniquely determined from a property name in the program in the first programming language; loading the interface class; and preparing, for a first class of the first programming language occurring during execution of the program in the first programming language, when the first class of the first programming language directly inherits a second class of the first programming language, a class hierarchy on the execution system of the second programming language so that the class hierarchy corresponds to a dynamically created class hierarchy on the program in the first programming language by caching a second class of the second programming language inheriting a first class of the second programming language, with the first class of the second programming language corresponding to the first class of the first programming language being a key; wherein fields are prepared in the first and second classes of the second programming language corresponding to the respective property declarations of the first and second classes of the program in the first programming language; and wherein a property access step via the interface classes is enabled by the classes of the second programming language prepared so as to implement the interface classes.