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Programs must not catch {{java.lang.NullPointerException}}. A {{NullPointerException}} exception thrown at runtime indicates the existence of an underlying {{null}} pointer dereference that must be fixed in the application code (see [EXP11-J. Never dereference null pointers|EXP11-J. Never dereference null pointers]). Handling the underlying null pointer dereference by catching the {{NullPointerException}} rather than fixing the underlying problem is inappropriate for several reasons. First, _avoiding_ the exception by catching {{NullPointerException}} adds significantly more performance overhead than simply adding the necessary checks \[[Bloch 2008|AA. Bibliography#Bloch 08]\]. Second, when there are multiple expressions in a {{try}} block that are capable of throwing a {{NullPointerException}}, it is difficult or impossible to determine which expression is responsible for the exception because the {{NullPointerException}} {{catch}} block handles any {{NullPointerException}} thrown from any location in the {{try}} block. Third, programs rarely remain in an expected and usable state after a {{NullPointerException}} has been thrown. Attempts to continue execution after first catching and logging (or worse, suppressing) the exception rarely succeed. |
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<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="7dfd79d35ba5c0ad-db80baf1-48c24c5c-87639574-367e96340156bbdef2928ef5"><ac:plain-text-body><![CDATA[ | [[J2SE 2011 | AA. Bibliography#J2SE 11]] | Catching Multiple Exception Types and Rethrowing Exceptions with Improved Type Checking | ]]></ac:plain-text-body></ac:structured-macro> | |
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ERR13-J. Do not throw RuntimeException, Exception, or Throwable 06. Exceptional Behavior (ERR) void ERR15-J. Do not catch NullPointerException07. Visibility and Atomicity (VNA)