public final FieldWriter visitField(
            final int access,
            final String name,
            final String descriptor) {
        FieldWriter fieldWriter =
                new FieldWriter(symbolTable, access, name, descriptor);
        if (firstField == null) {
            firstField = fieldWriter;
        } else {
            lastField.fv = fieldWriter;
        }
        return lastField = fieldWriter;
    }
The fields of this class, stored in a linked list of {@link FieldWriter} linked via their
{@link FieldWriter#fv} field. This field stores the last element of this list.
core/src/main/java/com/alibaba/fastjson2/internal/asm/ClassWriter.java