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If a finally clause is specified, irrespective 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 block blocks) executes to completion or not, normal completion. Statements that cause the finally block is executed. Consequently statements that abruptly exit from the finally block may cause thrown exceptions to be masked. Therefore, keywords like return, break, continue and throw should never be used within a finally block.

Noncompliant Code Example

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 Java Language Specification, §14.20.2, "Execution of try-finally and try-catch-finally" [JLS 2015]:

If execution of the try block completes abruptly for any other reason R, then the finally block is executed. Then there is a choice:

• If the finally block completes normally, then the try statement completes abruptly for reason R.
• If the finally block completes abruptly for reason S, then the try statement completes abruptly for reason S (and reason R is discarded).

Noncompliant Code Example

In this noncompliant code example, the finally block completes abruptly because of a return statement in the block:Here, the finally block completes abruptly since a return statement occurs within it. As a result, when the IllegalStateException is thrown, it does not propagate all the way up through the call stack. This is due to the abrupt termination of the finally block that suppresses any useful exception information from being displayed in the try block by overriding it with its own message. Note that even if the try block returns some value, the finally block is executed.

class TryFinally {              
  private static boolean doLogic() {
    try {
      throw new IllegalStateException(); 
    } 
    finally {
      System.out.println("Uncaughtlogic Exceptiondone");
      return true;
    }
  }
}

The IllegalStateException is suppressed by the abrupt completion of the finally block caused by the return statement.

Compliant Solution

This compliant solution removes the return statement from the finally block:

class TryFinally {
  publicprivate static voidboolean main(String[] args) doLogic() {
    try {
      throw new IllegalStateException();
    } finally {
    doLogic();	  System.out.println("logic done");
    }
    // Any return statements must go here; 
    // applicable only when exception is thrown conditionally
  }
}

Compliant Solution

Exceptions

ERRO4-J-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:This compliant solution removes the return statement from the finally block. Any return statements must occur after this block. In this example, the compiler will throw an error as the return statement is unreachable due to the explicit, unavoidable throwing of IllegalStateException. If the exception is thrown conditionally, the return statement can be used without any compilation errors.

class TryFinally {
  private static boolean doLogic() {
    try {
  private    staticthrow booleannew doLogicIllegalStateException();
    } finally {
      int c;
      try {
        while ((c = input.read()) != -1) {
         throw newif IllegalStateException(c > 128) {
            break;
          }
        }
      } catch (IOException x) {
    finally {    // Forward to handler
      }
      System.out.println("Caughtlogic Exceptiondone");
    }
    // anyAny return statements must go here
; applicable }

only when publicexception staticis void main(String[] args) {
    doLogic();	thrown conditionally
  }
}

Risk Assessment

Exiting abruptly from Abrupt completion of a finally block may lead to masking of thrown exceptionsmasks any exceptions thrown inside the associated try and catch blocks.

Automated Detection

...

TODO

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

References

\[[JLS 05|AA. Java References#JLS 05]\] [Section 14.20.2, Execution of try-catch-finally|http://java.sun.com/docs/books/jls/third_edition/html/statements.html#14.20.2]
\[[Bloch 05|AA. Java References#Bloch 05]\] Puzzle 36: Indecision
\[[Chess 07|AA. Java References#Chess 07]\] 8.2 Managing Exceptions, "The Vanishing Exception"
\[[MITRE 09|AA. Java References#MITRE 09]\] [CWE ID 705|http://cwe.mitre.org/data/definitions/705.html] "Incorrect Control Flow Scoping", [CWE ID 584|http://cwe.mitre.org/data/definitions/584.html] "Return Inside Finally Block"

Tool	Version	Checker	Description
Coverity	7.5	PW.ABNORMAL_TERMINATION_ OF_FINALLY_BLOCK	Implemented
Klocwork	Include Page Klocwork_V Klocwork_V	JD.FINRET
Parasoft Jtest	Include Page Parasoft_V Parasoft_V	CERT.ERR04.ARCF CERT.ERR04.ATSF	Avoid using 'return's inside 'finally blocks if thare are other 'return's inside the try-catch block Do not exit "finally" blocks abruptly
PVS-Studio	Include Page PVS-Studio_V PVS-Studio_V	V6051
SonarQube	Include Page SonarQube_V SonarQube_V	S1143	Jump statements should not occur in "finally" blocks

Related Guidelines

Bibliography

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Image Added Image Added Image AddedEXC04-J. Prevent against inadvertent calls to System.exit() or forced shutdown      10. Exceptional Behavior (EXC)      EXC31-J. Handle checked exceptions that can be thrown within a finally block