Early classes of the Java API, such as Vector, Hashtable and StringBuffer, were synchronized to make them
thread-safe. Unfortunately, synchronization has a big negative impact on performance, even when using these collections from a single thread.
It is better to use their new unsynchronized replacements:
-
ArrayList or LinkedList instead of Vector
-
Deque instead of Stack
-
HashMap instead of Hashtable
-
StringBuilder instead of StringBuffer
Even when used in synchronized context, you should think twice before using it, since it’s usage can be tricky. If you are confident the usage is
legitimate, you can safely ignore this warning.
Noncompliant Code Example
Vector cats = new Vector();
Compliant Solution
ArrayList cats = new ArrayList();
Exceptions
Use of those synchronized classes is ignored in the signatures of overriding methods.
@Override
public Vector getCats() {...}
