Java8新特性Optional类处理空值判断回避空指针异常应用

public class LoginUser implements UserDetails {
    private Long deptId;
    private String token;
    private Long loginTime;
    private Long expireTime;
    private String ipaddr;
    private String loginLocation;
    private String browser;
    private String os;
    private SysUser user;
}

public class SysUser {
    private Long userId;
    private Long deptId;
    private String userName;
}

public Long getUserId(LoginUser loginUser){
    if (loginUser!=null) {
        SysUser user = loginUser.getUser();
        if (user!=null) {
            return user.getUserId();
        }
    }
    return null;
}

public Long getUserId(LoginUser loginUser) {
    return Optional.ofNullable(loginUser)
        .map(LoginUser::getUser).map(SysUser::getUserId).orElse(null);
}