Never use return
, break
, continue
, or throw
statements within a finally
block. When program execution enters a try
block that has a finally
block, the finally
block always executes regardless of whether the try
block (or any associated catch
blocks) executes to normal completion. Statements that cause the finally
block to complete abruptly also cause the try
block to complete abruptly and consequently suppress any exception thrown from the try
or catch
blocks. According to the The Java Language Specification, §14.20.2, "Execution of try-finally
and try-catch-finally
" [JLS 20052015]:
If execution of the
try
block completes abruptly for any other reasonR
, then thefinally
block is executed. Then there is a choice:
- If the
finally
block completes normally, then thetry
statement completes abruptly for reasonR
.- If the
finally
block completes abruptly for reasonS
, then thetry
statement completes abruptly for reasonS
(and reasonR
is discarded).
Noncompliant Code Example
...
ERRO4-EX0: Control flow statements whose destination is within the finally
block are perfectly acceptable. For example, the following code does not violate this rule because the break
statement exits within the while
loop but not within the finally
block.:
Code Block | ||
---|---|---|
| ||
class TryFinally { private static boolean doLogic() { try { throw new IllegalStateException(); } finally { int c; try { while ((c = input.read()) != -1) { if (c > 128) { break; } } } catch (IOException x) { // Forward to handler } System.out.println("logic done"); } // Any return statements must go here; applicable only when exception is thrown conditionally } } |
...
Tool | Version | Checker | Description |
---|---|---|---|
Coverity | 7.5 | PW.ABNORMAL_TERMINATION_ OF_FINALLY_BLOCK | Implemented |
Related Guidelines
Bibliography
Puzzle 36. Indecision | |
Section 8.2, "Managing Exceptions, The Vanishing Exception" | |
...