Avoid usage of static collections.

If you want to use static collections make them final and create for example a singleton if needed containing the collections.

The static fields are more complicated for the Garbage Collector to manage and can lead to memory leaks.

Noncompliant Code Example

/**
 * Not compliant
 */
public class AvoidUsageOfStaticCollections {
    public static final List<> LIST = new ArrayList<>();
    public static final Set<> SET = new HashSet<>();
    public static final Map<> MAP = new HashMap<>();
}

Compliant Solution

/**
 * Compliant
 */
public class GoodUsageOfStaticCollections {
    public static volatile GoodUsageOfStaticCollections INSTANCE = new GoodUsageOfStaticCollections();

    public final List<> LIST = new ArrayList<>();
    public final Set<> SET = new HashSet<>();
    public final Map<> MAP = new HashMap<>();

    private GoodUsageOfStaticCollections() {
    }
}