1. A method to efficiently realize class initialization barriers in a multitasking virtual machine, wherein class loading always takes place before class initialization, and wherein a class initialization barrier guarantees that a class is initialized before the class is first used by a program, comprising: associating a shared runtime representation of the class with a task class mirror table that comprises at least one entry per-task, including an initialized entry, for a plurality of tasks, wherein each entry holds either a null pointer value or a non-null pointer to a task class mirror object, wherein all entries of a task mirror table that hold a non-null pointer value and that are associated with a same task hold a pointer to a same task class mirror object, wherein the task class mirror object holds a task private representation of the class for that task; using the initialized entry of a task in the task class mirror table to determine whether this task has initialized the class associated with the task class mirror table; and accessing the task class mirror object associated to a particular task.