Why is this an issue?
Since the introduction of generics in Java 5, the use of generic types such as List<String> is recommended over the use of raw
ones such as List. Assigning a raw type to a generic one is not type safe, and will generate a warning. The old EMPTY_...
fields of the Collections class return raw types, whereas the newer empty...() methods return generic ones.
Noncompliant code example
List<String> collection1 = Collections.EMPTY_LIST; // Noncompliant
Map<String, String> collection2 = Collections.EMPTY_MAP; // Noncompliant
Set<String> collection3 = Collections.EMPTY_SET; // Noncompliant
Compliant solution
List<String> collection1 = Collections.emptyList();
Map<String, String> collection2 = Collections.emptyMap();
Set<String> collection3 = Collections.emptySet();
