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The user is allowed to access files in only the user-specific directory so no file system information is leaked in the process (EXC06-J. Do not allow exceptions to transmit sensitive information).

Noncompliant Code Example

It is not possible to propagate a checked exception by throwing it from a Runnable object's run() method. Consequently, this noncompliant code example catches java.lang.InterruptedException but ignores it.

class Foo implements Runnable {
  public void run() {
    try {
      Thread.sleep(1000);    
    } catch(InterruptedException e) {
      // Ignore
    }
  }
}

Any callers higher up in the call stack are unable to determine that an interrupted exception occurred and act on it \[[Goetz 06|AA. Java References#Goetz 06]\].

Compliant Solution

This compliant solution catches the InterruptedException and restores the interrupted status by calling the interrupt() method on the current thread.

class Foo implements Runnable {
  public void run() {
    try {
      Thread.sleep(1000);    
    } catch(InterruptedException e) {
      Thread.currentThread().interrupt(); // Reset interrupted status
    }
  }
}

Consequently, code that is higher up on the call stack can see that an interrupt was issued \[[Goetz 06|AA. Java References#Goetz 06]\].

Exceptions

EX1: It is reasonable to ignore handling an exception that occurs within a catch or finally block, such as when closing a FileInputStream object.

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try {
  // Requested file does not exist
  // User is unable to supply the file name
} catch(FileNotFoundException e) { 
  throw new RuntimeException(e);
}

*EX3:* "The only situation in which it is acceptable to swallow an interrupt is when you are extending Thread and therefore control all the code higher up on the call stack." \[[Goetz 06|AA. Java References#Goetz 06]\]. In such cases {{InterruptedException}} may be caught and ignored.

Risk Assessment

Ignoring or suppressing exceptions violates the fail-safe criteria of an application.

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\[[JLS 05|AA. Java References#JLS 05]\] [Chapter 11, Exceptions|http://java.sun.com/docs/books/jls/third_edition/html/exceptions.html]
\[[Bloch 08|AA. Java References#Bloch 08]\] Item 65: "Don't ignore exceptions", Item 62: "Document all exceptions thrown by each method"
\[[Goetz 06|AA. Java References#Goetz 06]\] 5.4 Blocking and interruptible methods
\[[MITRE 09|AA. Java References#MITRE 09]\]  [CWE ID 390|http://cwe.mitre.org/data/definitions/390.html] "Detection of Error Condition Without Action"

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