Set object value changes null value object

List<ShangpinInfoVODTO> footers= baseShangpinMapper.selectShangpinPageFooterList(term,wrapper);
fillFootersKcJeByKhJgsd( khdm,footers);
log("footers",footers,true);

    protected void fillFootersKcJeByKhJgsd(String khdm,List<ShangpinInfoVODTO> footers) throws Exception{
        String jgsd=baseKehuService.getJgsd2VOByKhdm(khdm).getJgsd();
        fillFootersKcJeByJgsd( jgsd,footers);
    }
    protected void fillFootersKcJeByJgsd(String jgsd,List<ShangpinInfoVODTO> footers) throws Exception{
        for(ShangpinInfoVODTO vo:footers){
            log("vo1", vo, true);
            if(null==vo) {
                vo=new ShangpinInfoVODTO();
                vo.setKcsl(0);
                vo.setKcje(0.0);

            }else{
                switch(jgsd){
                    case "BZSJ":vo.setKcje(vo.getBzsje()); break;
                    case "SJ1": vo.setKcje(vo.getSj1e()); break;
                    case "SJ2": vo.setKcje(vo.getSj2e()); break;
                    case "SJ3": vo.setKcje(vo.getSj3e()); break;
                    case "SJ4": vo.setKcje(vo.getSj4e()); break;
                    case "4":vo.setKcje(vo.getBzsje()); break;
                    case "5": vo.setKcje(vo.getSj1e()); break;
                    case "6": vo.setKcje(vo.getSj2e()); break;
                    case "7": vo.setKcje(vo.getSj3e()); break;
                    case "8": vo.setKcje(vo.getSj4e()); break;
                    default:break;
                }
            }
            if(null==vo.getKcsl()) vo.setKcsl(0);
            if(null==vo.getKcje()) vo.setKcje(0.0);
            log("vo2", vo, true);
        }
        log("footers1", footers, true);
    }

Print the results ：

2022-06-30 10:08:39.419  INFO 1376 --- [io-18089-exec-2] com.hieasy.comm.util.BaseUtil            : vo1:null
2022-06-30 10:08:39.419  INFO 1376 --- [io-18089-exec-2] com.hieasy.comm.util.BaseUtil            : vo2:{"guige1List":[],"kcje":0.0,"kcsl":0,"limitKcys":0,"limitKcysType":0,"picList":[]}
2022-06-30 10:08:39.419  INFO 1376 --- [io-18089-exec-2] com.hieasy.comm.util.BaseUtil            : footers1:[null]
2022-06-30 10:08:39.430  INFO 1376 --- [io-18089-exec-2] com.hieasy.comm.util.BaseUtil            : footers:[null]
 

From the print results , Collection null value new The value of , Cannot change the object

It needs to be replaced with the following code ：

  protected void fillFootersKcJeByKhJgsd(String khdm,List<ShangpinInfoVODTO> footers) throws Exception{
        String jgsd=baseKehuService.getJgsd2VOByKhdm(khdm).getJgsd();
        fillFootersKcJeByJgsd( jgsd,footers);
    }
    protected void fillFootersKcJeByJgsd(String jgsd,List<ShangpinInfoVODTO> footers) throws Exception{
        for (int i = 0; i < footers.size(); i++) {
            ShangpinInfoVODTO sp= footers.get(i);
            if(null==sp) {
                sp=new ShangpinInfoVODTO();
                sp.setKcsl(0);
                sp.setKcje(0.0);
                footers.set(i, sp);
            }else{
                switch(jgsd){
                    case "BZSJ":sp.setKcje(sp.getBzsje()); break;
                    case "SJ1": sp.setKcje(sp.getSj1e()); break;
                    case "SJ2": sp.setKcje(sp.getSj2e()); break;
                    case "SJ3": sp.setKcje(sp.getSj3e()); break;
                    case "SJ4": sp.setKcje(sp.getSj4e()); break;
                    case "4":sp.setKcje(sp.getBzsje()); break;
                    case "5": sp.setKcje(sp.getSj1e()); break;
                    case "6": sp.setKcje(sp.getSj2e()); break;
                    case "7": sp.setKcje(sp.getSj3e()); break;
                    case "8": sp.setKcje(sp.getSj4e()); break;
                    default:break;
                }
            }
        }
        log("footers1", footers, true);
    }

Print the results ：

 2022-06-30 10:19:36.651  INFO 8584 --- [io-18089-exec-2] com.hieasy.comm.util.BaseUtil            : footers1:[{"guige1List":[],"kcje":0.0,"kcsl":0,"limitKcys":0,"limitKcysType":0,"picList":[]}]