ShortenFullyQualifiedTypeReferences does not shorten java.lang

Currently, ShortenFullyQualifiedTypeReferences does not shorten all types:

class TestClass {
    java.util.List<java.lang.Enum> foo;
}

in combination with ShortenFullyQualifiedTypeReferences leads to

class TestClass {
    List<java.lang.Enum> foo;
}

A change like the following to the visitor in ShortenFullyQualifiedTypeReferences,

@Override
public J.Identifier visitIdentifier(J.Identifier identifier, Map<String, JavaType> types) {
    JavaType type = identifier.getType();
    if (type instanceof JavaType.FullyQualified && identifier.getFieldType() == null) {
        types.put(identifier.getSimpleName(), type);
    }
    // ==========
    if (type instanceof JavaType.Parameterized param) {
        types.put(param.getClassName(), param.getType());
        for (var typeParams : param.getTypeParameters()) {
            if (typeParams instanceof JavaType.FullyQualified fq) {
                types.put(fq.getClassName(), fq);
            }
        }
    }
    // ==========
    return identifier;
}

fixes the issue for me.

Note that it already works if there is an explicit field of type Enum.

Start by locating the ShortenFullyQualifiedTypeReferences visitor and its visitIdentifier method. Reproduce the issue with the Java snippet in the report, then inspect how parameterized type arguments such as java.lang.Enum are collected. Done means the recipe shortens both java.util.List and java.lang.Enum in the example without regressing explicit Enum fields.