Primitives should be "volatile"

Primitives can be read and written to atomically. Except for long and double, that is. These 64-bit primitives must be marked volatile in multi-threaded environments, or swapped out for their atomic counterparts: AtomicLong, and AtomicDouble to guarantee that their updates are always visible to other threads.

Similarly, to ensure that updates to 32-bit primitives are visible to all threads, they should also be marked volatile.

Noncompliant Code Example

long m = 0;  // Noncompliant

public void increment() {
  m++;
}

Compliant Solution

volatile long m = 0;

public void increment() {
  m++;
}

or

AtomicLong m = new AtomicLong(0);

public void increment() {
  m.incrementAndGet();
}

See

• CERT, VNA00-J. - Ensure visibility when accessing shared primitive variables
• CERT, VNA05-J. - Ensure atomicity when reading and writing 64-bit values