实体类

public class Sp {
    String spdm;
    String spmc;

    public Sp() {
    }

    public Sp(String spdm, String spmc) {
        this.spdm = spdm;
        this.spmc = spmc;
    }

    public String getSpdm() {
        return spdm;
    }

    public void setSpdm(String spdm) {
        this.spdm = spdm;
    }

    public String getSpmc() {
        return spmc;
    }

    public void setSpmc(String spmc) {
        this.spmc = spmc;
    }
}

list

    public static void main(String[] args) {
        List<Sp> sps=new ArrayList<>();
        Sp sp1=new Sp("01","商品1");
        Sp sp2=new Sp("02","商品2");
        Sp sp3=new Sp("03","商品3");
        Sp sp4=new Sp("04","商品4");
        Sp sp5=new Sp("05","商品5");
        sps.add(sp1);
        sps.add(sp2);
        sps.add(sp3);
        sps.add(sp4);
        sps.add(sp5);

        List<String> spdms=sps.stream().map(u->u.getSpdm()).collect(Collectors.toList());
        System.out.println(spdms);
    }

结果