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 completion. Statements that cause the {{finally}} block to terminate abruptly also cause the {{try}} block to terminate abruptly and consequently mask any exception thrown from the {{try}} or {{catch}} blocks \[[JLS 2005|http://java.sun.com/docs/books/jls/third_edition/html/statements.html#14.20.2]\].

Noncompliant Code Example

In this noncompliant code example, the finally block completes abruptly because of a return statement in the block.

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

  public static void main(String[] args) {
    doLogic();
  }
}

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

Compliant Solution

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

class TryFinally {
  private static boolean doLogic() {
    try {
      throw new IllegalStateException();
    } finally {
      System.out.println("Caught Exception");
    }
    // Any return statements must go here; applicable only when exception is thrown conditionally
  }

  public static void main(String[] args) {
    doLogic();
  }
}

Risk Assessment

Exiting abruptly from a finally block masks any exceptions thrown inside the associated try and catch blocks.

Recommendation

Severity

Likelihood

Remediation Cost

Priority

Level

ERR04-J

low

probable

medium

P4

L3

Related Vulnerabilities

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

Bibliography

\[[Bloch 2005|AA. Bibliography#Bloch 05]\] Puzzle 36: Indecision
\[[Chess 2007|AA. Bibliography#Chess 07]\] 8.2 Managing Exceptions, "The Vanishing Exception"
\[[JLS 2005|AA. Bibliography#JLS 05]\] [§14.20.2, Execution of try-catch-finally|http://java.sun.com/docs/books/jls/third_edition/html/statements.html#14.20.2]
\[[MITRE 2009|AA. Bibliography#MITRE 09]\] [CWE-705|http://cwe.mitre.org/data/definitions/705.html] "Incorrect Control Flow Scoping" and [CWE-584|http://cwe.mitre.org/data/definitions/584.html] "Return Inside Finally Block"

      06. Exceptional Behavior (ERR)