Possibly null fields should not be synchronized on JAVA-E1060

There is a null check for a field which is being synchronized on. Since the field is synchronized on, it is unlikely that it will be null. If it is null and then synchronized on, a NullPointerException will be thrown on synchronization and the check would be pointless.

Bad Practice

// may throw NPE.
synchronize(possiblyNull) {
    if (possiblyNull != null) {
        // ...
    }
}

Recommended

synchronize(nonNull) {
    if (possiblyNull != null) {
        // ...
    }
}

Avoid structuring your code in a way that allows for nullable values to be used in a non-null context.

References

• CWE-476 - Null Pointer Dereference
• CWE-667 - Improper Locking
• Spotbugs - NP_SYNC_AND_NULL_CHECK_FIELD