According to the Java Language Specification [JLS 2011], §8.3.1.4, "volatile Fields" [JLS 2011],"
A field may be declared
volatile, in which case the Java Memory Model ensures that all threads see a consistent value for the variable (§17.4).
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This noncompliant code example attempts to use the volatile-read, synchronized-write technique described by Goetz in Java Theory and Practice [Goetz 2007]. The map field is declared volatile to synchronize its reads and writes. The put() method is also synchronized to ensure that its statements are executed atomically.
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Because DateFormat is not thread-safe [API 2011], the value for Date returned by the parse() method might fail to correspond to the str argument.:
Compliant Solution (Instance per Call/Defensive Copying)
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