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Reference.org
Phantom reference
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<p>A phantom reference is a kind of reference in <a href="/facts/Java_/9ScgFyAL">Java</a>, where the memory can be reclaimed. The phantom reference is one of the strengths or levels of 'non <a href="/facts/Strong_reference/TCnnws7x">strong</a>' reference defined in the Java programming language; the others being <a href="/facts/Weak_reference/TCnnws7x">weak</a> and <a href="/facts/Soft_reference/3CLjNUF0">soft</a>. Phantom reference are the weakest level of reference in Java; in order from strongest to weakest, they are: strong, soft, weak, <i>phantom.</i> </p><p>An object is phantomly referenced after it has been <a href="/facts/Finalizer/6vU0SvEb">finalized</a>. </p><p>In Java 8 and earlier versions, the reference needs to be cleared before the memory for a finalized referent can be reclaimed. A change in Java 9 will allow memory from a finalized referent to be reclaimable immediately. </p>