A method and system for class loading in a Java Virtual Machine (JVM) environment. Specifically, the system includes a code-source index and a mapper. The code-source index is associated with at least one class loader in a class loader tree in the JVM environment. The code-source index includes a plurality of parameters for cross-referencing packages in the at least one class loader to code-sources. The system also includes a mapper for referencing the code-source index. That is, the mapper maps a package associated with a class to one or more associated code-sources that potentially can access the class in the class loader tree.