CON05-J. Ensure that threads do not fail during activation

It is critical to ensure that threads are activated correctly. Thread activation can be misleading because sometimes the code appears to be performing the function correctly, whereas it may be operating in the presence of subtle concurrency issues.

Noncompliant Code Example

The run() method of interface Runnable must be invoked in its own thread, however, this noncompliant code example explicitly invokes it in the context of the current thread.

class Foo implements Runnable {
  public void run() {
    // ...
  }
  
  public static void main(String[] args) {
    Foo f = new foo();
    new Thread(f).run();
  }
}

The start() method is not invoked on the new thread because of the incorrect assumption that run() activates the thread. Consequently, the statements in the run() method execute, however, in the same thread instead of the new one.

Compliant Solution

This compliant solution correctly uses the start() method to start a new thread which then executes the run() method.

class Foo implements Runnable {
  public void run() {
    // ...
  }
  
  public static void main(String[] args) {
    Foo f = new foo();
    new Thread(f).start();
  }
}

Risk Assessment

Failing to activate threads correctly can cause unexpected behavior.

Automated Detection

TODO

Related Vulnerabilities

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

References

[[API 06]] Interface Runnable and class Thread

CON04-J. Use the private lock object idiom instead of the object's intrinsic locking mechanism      11. Concurrency (CON)      CON06-J. Do not defer a thread that is holding a lock