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 _Java Language Specification_, [§14.20.2, Execution of try-catch-finally|http://java.sun.com/docs/books/jls/third_edition/html/statements.html#14.20.2] \[[JLS 2005|AA. References#JLS 05]\]:

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

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

Exceptions

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 the while loop, but not the finally 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
  }
}

Risk Assessment

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

Rule

Severity

Likelihood

Remediation Cost

Priority

Level

ERR04-J

low

probable

medium

P4

L3

Related Guidelines

MITRE CWE

CWE-459. Incomplete cleanup

 

CWE-584. Return inside finally block

Bibliography

<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="e914baec-aa07-4913-b680-833cf1a00e18"><ac:plain-text-body><![CDATA[

[[Bloch 2005

AA. References#Bloch 05]]

Puzzle 36. Indecision

]]></ac:plain-text-body></ac:structured-macro>

<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="a0580985-97f2-4735-a724-d013aec062b0"><ac:plain-text-body><![CDATA[

[[Chess 2007

AA. References#Chess 07]]

8.2, Managing Exceptions, The Vanishing Exception

]]></ac:plain-text-body></ac:structured-macro>

<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="679a946f-7b38-4901-9d18-a348f700a778"><ac:plain-text-body><![CDATA[

[[JLS 2005

AA. References#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]

]]></ac:plain-text-body></ac:structured-macro>

      06. Exceptional Behavior (ERR)