一种极其优雅的操作两个对象类的统计等操作——博主备忘

package net.xdclass.vo;

import com.fasterxml.jackson.annotation.JsonProperty;
import io.swagger.models.auth.In;

import java.math.BigDecimal;
import java.util.List;



public class CartVO {

    /**
     * 购物项
     */
    @JsonProperty("cart_items")
    private List<CartItemVO> cartItems;


    /**
     * 购买总件数
     */
    @JsonProperty("total_num")
    private Integer totalNum;

    /**
     * 购物车总价格
     */
    @JsonProperty("total_price")
    private BigDecimal totalPrice;

    /**
     * 购物车实际支付价格
     */
    @JsonProperty("real_pay_price")
    private BigDecimal realPayPrice;


    /**
     * 总件数
     * @return
     */
    public Integer getTotalNum() {
        if(this.cartItems!=null){
            int total = cartItems.stream().mapToInt(CartItemVO::getBuyNum).sum();
            return total;
        }
        return 0;
    }

    /**
     * 总价格
     * @return
     */
    public BigDecimal getTotalPrice() {
        BigDecimal amount = new BigDecimal("0");
        if(this.cartItems!=null){
            for(CartItemVO cartItemVO : cartItems){
                BigDecimal itemTotalAmount =  cartItemVO.getTotalAmount();
                amount = amount.add(itemTotalAmount);
            }
        }
        return amount;
    }

    /**
     * 购物车里面实际支付的价格
     * @return
     */
    public BigDecimal getRealPayPrice() {
        BigDecimal amount = new BigDecimal("0");
        if(this.cartItems!=null){
            for(CartItemVO cartItemVO : cartItems){
                BigDecimal itemTotalAmount =  cartItemVO.getTotalAmount();
                amount = amount.add(itemTotalAmount);
            }
        }
        return amount;
    }

    public List<CartItemVO> getCartItems() {
        return cartItems;
    }

    public void setCartItems(List<CartItemVO> cartItems) {
        this.cartItems = cartItems;
    }
}

package net.xdclass.vo;

import com.fasterxml.jackson.annotation.JsonProperty;

import java.math.BigDecimal;



public class CartItemVO {

    /**
     * 商品id
     */
    @JsonProperty("product_id")
    private Long productId;


    /**
     * 购买数量
     */
    @JsonProperty("buy_num")
    private Integer buyNum;

    /**
     * 商品标题
     */
    @JsonProperty("product_title")
    private String productTitle;

    /**
     * 图片
     */
    @JsonProperty("product_img")
    private String productImg;

    /**
     * 商品单价
     */
    private BigDecimal amount;

    /**
     * 总价格，单价+数量
     */
    @JsonProperty("total_amount")
    private BigDecimal totalAmount;


    public Long getProductId() {
        return productId;
    }

    public void setProductId(Long productId) {
        this.productId = productId;
    }

    public Integer getBuyNum() {
        return buyNum;
    }

    public void setBuyNum(Integer buyNum) {
        this.buyNum = buyNum;
    }

    public String getProductTitle() {
        return productTitle;
    }

    public void setProductTitle(String productTitle) {
        this.productTitle = productTitle;
    }

    public String getProductImg() {
        return productImg;
    }

    public void setProductImg(String productImg) {
        this.productImg = productImg;
    }

    public BigDecimal getAmount() {
        return amount;
    }

    public void setAmount(BigDecimal amount) {
        this.amount = amount;
    }

    /**
     * 商品单价 * 购买数量
     * @return
     */
    public BigDecimal getTotalAmount() {

        return this.amount.multiply(new BigDecimal(this.buyNum));
    }

}

    /**
     * 总件数
     * @return
     */
    public Integer getTotalNum() {
        if(this.cartItems!=null){
            int total = cartItems.stream().mapToInt(CartItemVO::getBuyNum).sum();
            return total;
        }
        return 0;
    }

    /**
     * 总价格
     * @return
     */
    public BigDecimal getTotalPrice() {
        BigDecimal amount = new BigDecimal("0");
        if(this.cartItems!=null){
            for(CartItemVO cartItemVO : cartItems){
                BigDecimal itemTotalAmount =  cartItemVO.getTotalAmount();
                amount = amount.add(itemTotalAmount);
            }
        }
        return amount;
    }