Java8统计金额demo

package com.example.core.mydemo.java8;

public class GoodsPriceDTO {
    private String goodName;
    private Integer amount;

    public String getGoodName() {
        return goodName;
    }

    public void setGoodName(String goodName) {
        this.goodName = goodName;
    }

    public Integer getAmount() {
        return amount;
    }

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

package com.example.core.mydemo.java8;

import java.util.ArrayList;
import java.util.List;
import java.util.Optional;

public class GoodsTotalTest {
    public static void main(String[] args) {
        List<GoodsPriceDTO> goodsPriceDTOS = new ArrayList<GoodsPriceDTO>();
        GoodsPriceDTO dto = new GoodsPriceDTO();
        dto.setGoodName("Apple");
        dto.setAmount(27);
        goodsPriceDTOS.add(dto);

        dto = new GoodsPriceDTO();
        dto.setGoodName("Orange");
        dto.setAmount(28);
        goodsPriceDTOS.add(dto);

        dto = new GoodsPriceDTO();
        dto.setGoodName("Banana");
        dto.setAmount(29);
        goodsPriceDTOS.add(dto);

        dto = new GoodsPriceDTO();
        dto.setGoodName("Apple");
        dto.setAmount(23);
        goodsPriceDTOS.add(dto);

        
        int amt = Optional.ofNullable(goodsPriceDTOS)
                .orElseGet(ArrayList::new)
                .stream()
                .filter(x -> x != null && ("Apple".equals(x.getGoodName()))).mapToInt(GoodsPriceDTO::getAmount).sum();
        System.out.println("amt=" + amt);
    }
}