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Because, the field is nonvolatile and nonfinal, the statements within the constructor can be reordered by the compiler in such a way that the this reference is published before the initialization statements have executed.
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Compliant Solution (volatile and publish after initialization)
This noncompliant code example declares the pub field as volatile and reduces the accessibility of the static class field to package-private so that untrusted callers beyond the current package cannot obtain the this reference.
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