java - Arraylist 删除第一次出现，而不是一个确切的对象

Question

我在 jsf 中有数据表。单击添加按钮后，根据所选值加载列表。元素已成功添加到列表中。 添加到列表中，

public class CompanyProduct implements Serializable{
    private static final long serialVersionUID = 1L;

        @Id
        @GeneratedValue
        @Getter @Setter private int id;

        @ManyToOne
        @JoinColumn(name = "productId", referencedColumnName = "id")
        @Getter @Setter private Product product;

        @ManyToOne
        @JoinColumn(name = "companyId", referencedColumnName = "id")
        @Getter @Setter private Company company;

        @Setter @Getter private Double price;

        @Setter @Getter private Double sellingprice;

        @Column
        @Getter @Setter private Integer minQuantity;

        @Column
        @Getter @Setter private Integer maxQuantity;

        @Column
        @Getter @Setter private Integer leadTime;

        @ManyToOne
        @JoinColumn(name="uom_group_item_id")
        @Getter @Setter private UomGroupItem uomGroupItem;

}

public void addToAssociation() {


        List<CompanyProduct> tmpList = new ArrayList<CompanyProduct>(companyproducts);

        for (Product p : selectedProducts) {
            boolean flag = false;

            for(CompanyProduct companyProduct: tmpList){
                if(companyProduct.getUomGroupItem() == null && companyProduct.getProduct() != null && companyProduct.getProduct().getId().equals(p.getId())){
                    flag = true;
                }
            }

            if(!flag){
                addCompanyProducts(p, null);
            }

            addUomGroupProduct(p);
        }
        selectedProducts = null;
        loadLazyProducts();
    }

private void addCompanyProducts(Product p,UomGroupItem item){
        CompanyProduct sg = new CompanyProduct();
        sg.setProduct(p);
        sg.setCompany(company);
        sg.setPrice((double) (p.getMrp()==null?0f:p.getMrp()));
        sg.setSellingprice((double) (p.getMrp()==null?0f:p.getMrp()));

        if(item != null){
            sg.setUomGroupItem(item);
        }

        companyproducts.add(sg);
    }

但问题是，当我删除时，正在执行操作，

for (CompanyProduct sg : selectedToBeAssociatedProducts) {
        companyproducts.remove(sg);
    }

但它删除了列表中的第一次出现。所以我可以知道这个问题的原因吗？提前致谢。

如有任何疑问，请告诉我。

Answer 1

这是设计使然，请参阅 List API

remove(Object o) 

Removes the first occurrence of the specified element from this list, if it is present (optional operation).

如果你想删除所有出现的地方，使用 List.removeAll，像这样

list.removeAll(Collectoins.singelton(obj);