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Reference.org
Void safety
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<p>Void safety (also known as null safety) is a guarantee within an <a href="/facts/Object-oriented_language/TxNMEcao">object-oriented programming language</a> that no <a href="/facts/Reference_(computer_science)/1vm2Bph1">object references</a> will have <a href="/facts/Null_pointer/66zwVEfL"><i>null</i> or <i>void</i></a> values. </p><p>In object-oriented languages, access to objects is achieved through <a href="/facts/Reference_(computer_science)/1vm2Bph1">references</a> (or, equivalently, <a href="/facts/Pointer_(computer_programming)/fPoNzy9b">pointers</a>). A typical call is of the form: </p> x.f(a, ...) <p>where <i>f</i> denotes an operation and <i>x</i> denotes a reference to some object. At execution time, however, a reference can be <i>void</i> (or <i>null</i>). In such cases, the call above will be a void call, leading to a run-time <a href="/facts/Exception_handling/VrJxgb9r">exception</a>, often resulting in <a href="/facts/Crash_(computing)/I8yn65yt">abnormal termination</a> of the program. </p><p>Void safety is a static (compile-time) guarantee that a void call will never arise. </p>