1. A method, performed by a data processing system comprising a memory, for just-in-time instrumentation, the method comprising: responsive to a class loading a hook for a probe, creating a static class information object that stores static information for the class; inserting a reference to the hook in metadata of the class; and inserting a reference to the static class information object in the metadata of the class, wherein the static class information object comprises a reference to the probe, wherein the creating of the static class information object, the inserting of the reference to the hook and the inserting of the reference to the static class information object are all performed by the data processing system using the memory.