import java.util.HashSet; class Issue { public void some(String group) { new HashSet<Permission>().stream() .map(permission -> (PrincipalPermission) permission) .filter(permission -> group.equals(permission.getGroup())); } } class Permission { } class PrincipalPermission<<warning descr="Type parameter 'T' is never used">T</warning>> extends Permission { public String getGroup() { return null; } }