...
This noncompliant code example shows a thread that fills a vector with pseudorandom numbers. The thread is forcefully stopped after a given amount of time.
| Code Block | ||
|---|---|---|
| ||
public final class Container implements Runnable {
private final Vector<Integer> vector = new Vector<Integer>(1000);
public Vector<Integer> getVector() {
return vector;
}
@Override public synchronized void run() {
Random number = new Random(123L);
int i = vector.capacity();
while (i > 0) {
vector.add(number.nextInt(100));
i--;
}
}
public static void main(String[] args) throws InterruptedException {
Thread thread = new Thread(new Container());
thread.start();
Thread.sleep(5000);
thread.stop();
}
}
|
...
This compliant solution uses a volatile flag to request thread termination. The shutdown() accessor method is used to set the flag to true. The thread's run() method polls the done flag and terminates when it is set.
| Code Block | ||
|---|---|---|
| ||
public final class Container implements Runnable {
private final Vector<Integer> vector = new Vector<Integer>(1000);
private volatile boolean done = false;
public Vector<Integer> getVector() {
return vector;
}
public void shutdown() {
done = true;
}
@Override public synchronized void run() {
Random number = new Random(123L);
int i = vector.capacity();
while (!done && i > 0) {
vector.add(number.nextInt(100));
i--;
}
}
public static void main(String[] args) throws InterruptedException {
Container container = new Container();
Thread thread = new Thread(container);
thread.start();
Thread.sleep(5000);
container.shutdown();
}
}
|
...
In this compliant solution, the Thread.interrupt() method is called from main() to terminate the thread. Invoking Thread.interrupt() sets an internal interrupt status flag. The thread polls that flag using the Thread.interrupted() method, which both returns true if the current thread has been interrupted and clears the interrupt status flag.
| Code Block | ||
|---|---|---|
| ||
public final class Container implements Runnable {
private final Vector<Integer> vector = new Vector<Integer>(1000);
public Vector<Integer> getVector() {
return vector;
}
@Override public synchronized void run() {
Random number = new Random(123L);
int i = vector.capacity();
while (!Thread.interrupted() && i > 0) {
vector.add(number.nextInt(100));
i--;
}
}
public static void main(String[] args) throws InterruptedException {
Container c = new Container();
Thread thread = new Thread(c);
thread.start();
Thread.sleep(5000);
thread.interrupt();
}
}
|
...
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
THI05-J | low | probable | medium | P4 | L3 |
Related Guidelines
POS47-C. Do not use threads that can be canceled asynchronously | |
CWE-705. Incorrect Control Flow Scoping |
Android Implementation Details
On Android, Thread.stop() was deprecated in API level 1.
Bibliography
[API 2006] | Class |
[Sun 1999] |
|
24.3, Stopping a Thread | |
Concurrency Utilities, More information: Java Thread Primitive Deprecation | |
[JPL 2006] | 14.12.1, Don't Stop; 23.3.3, Shutdown Strategies |
2.4, Two Approaches to Stopping a Thread | |
Chapter 7, Cancellation and Shutdown |