The java::isnull command is used to tell if a Java reference has the null value. The javaObj argument specifies an object handle. If the object has the null value, java::isnull will return 1. If the object is a Java object then java::isnull will return 0. If the object is not a valid Java object but rather a standard Tcl string, java::isnull will return an error stating that the argument was not a Java object handle.
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