atomicity : When applied to an operation on primitive data, indicates that other threads that might access the data might see the data as it exists before the operation occurs or after the operation has completed, but may never see an intermediate value of the data.
trusted code : Code that is loaded by the primordial class loader, irrespective of whether it constitutes the Java API or not. In this text, this meaning is extended to include code that is obtained from a known entity and given permissions that untrusted code lacks. By this definition, untrusted and trusted code can coexist in the namespace of a single class loader (not necessarily the primordial class loader). In such cases, the security policy must make this distinction clear by assigning appropriate privileges to trusted code, while denying the same from untrusted code.
untusted code : Code of unknown origin that can potentially cause some harm when executed. Untrusted code may not always be malicious but this is usually hard to determine automatically. Consequently, untrusted code should be run in a sandboxed environment.
volatile : (http://mindprod.com/jgloss/volatile.html
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The volatile keyword is used on variables that may be modified simultaneously by other threads. This warns the compiler to fetch them fresh each time, rather than caching them in registers. This also inhibits certain optimisations that assume no other thread will change the values unexpectedly. Since other threads cannot see local variables, there is never any need to mark local variables volatile. You need synchronized to co-ordinate changes to variables from different threads, but often volatile will do just to look at them. volatile does not guarantee you atomic access, e.g. a ++;
This is similar to, but distinct from the volatile keyword as used in C and C++.