list中将具有对应字段的某一个对象放在第一个

public class Demo {
   
    private Integer id;
    private Integer num;

    public Demo() {
   

    }

    public Integer getId() {
   
        return id;
    }

    public void setId(Integer id) {
   
        this.id = id;
    }

    public Integer getNum() {
   
        return num;
    }

    public void setNum(Integer<