java - 将两个数组列表中的值相加并返回第三个列表

Question

如果存在于两个列表中，则通过总结与相同元素相关的数据来创建第三个数组列表，否则插入新数据

我从两个数组列表中创建了两个映射，并将 Id 作为键，然后通过组合两个映射中的键创建了一个集合。利用集合中的值，我查询了两个列表并得出了总和。如果我遵循此方法，我会看到预期的输出，但想知道在 Java 1.6 中是否有任何其他有效的方法来实现此目的

----------------Java----------------

public class Stock {

    private int stockCode;
    private int stockQuantity;
    private int stockValue;

    public int getStockCode() {
        return stockCode;
    }

    public int getStockQuantity() {
        return stockQuantity;
    }

    public int getStockValue() {
        return stockValue;
    }

    public Stock(int stockCode, int stockQuantity, int stockValue) {
        this.stockCode = stockCode;
        this.stockQuantity = stockQuantity;
        this.stockValue = stockValue;
    }

    public static void main(String[] args){
        List<Stock> oldStock = new ArrayList<Stock>();
        Stock s1 = new Stock(1,  20, 16000);
        Stock s2 = new Stock(2, 10, 5000);
        Stock s3 = new Stock(3,  15, 3000);
        oldStock.add(s1);
        oldStock.add(s2);
        oldStock.add(s3);

        List<Stock> newStock = new ArrayList<Stock>();
        Stock s4 = new Stock(5, 5, 2500);
        Stock s5 = new Stock(1, 10, 8000);
        Stock s6 = new Stock(3, 10, 2000);
        newStock.add(s4);
        newStock.add(s5);
        newStock.add(s6);

        List<Stock> netStock = new ArrayList<Stock>();

        Map<Integer, Stock> oldStockMap = new HashMap<Integer, Stock>();
        for(Stock os:oldStock){
            oldStockMap.put(os.getStockCode(),os);
        }
        Map<Integer, Stock> newStockMap = new HashMap<Integer, Stock>();
        for(Stock ns:newStock){
            newStockMap.put(ns.getStockCode(),ns);
        }
        Set<Integer> keySet = new HashSet<Integer>();
        keySet.addAll(oldStockMap.keySet());
        keySet.addAll(newStockMap.keySet());

        for(Integer ks:keySet){
            Integer netStockQ=0;
            Integer netStockV=0;
            if(oldStockMap.get(ks)!=null && newStockMap.get(ks)!=null) {
                netStockQ =oldStockMap.get(ks).getStockQuantity() + newStockMap.get(ks).getStockQuantity();
                netStockV = oldStockMap.get(ks).getStockValue() + newStockMap.get(ks).getStockValue();
            } else if(oldStockMap.get(ks)==null && newStockMap.get(ks)!=null){
                netStockQ = newStockMap.get(ks).getStockQuantity();
                netStockV = newStockMap.get(ks).getStockValue();
            } else if(oldStockMap.get(ks)!=null && newStockMap.get(ks)==null){
                netStockQ =oldStockMap.get(ks).getStockQuantity();
                netStockV = oldStockMap.get(ks).getStockValue();
            }
            netStock.add(new Stock(ks,netStockQ, netStockV));
        }

        for(Stock ns: netStock){
            System.out.println(ns.getStockCode() +"- Quantity - "+ ns.getStockQuantity()+"- Value -"+ns.getStockValue());
        }
    }
}

----------------输出----------------

1- Quantity - 30- Value -24000
2- Quantity - 10- Value -5000
3- Quantity - 25- Value -5000
5- Quantity - 5- Value -2500

Answer 1

您可以执行以下操作(假设您无法升级到 Java 8)

• 创建一个以股票代码为键，股票为值的映射

Map<Integer, Stock> netStockMap = new HashMap<Integer, Stock>();

• 然后将所有旧库存条目添加到该 map ，如下所示。

for (Stock oldStockItem: oldStock) {
    netStockMap.put(oldStockItem.getStockCode(), oldStockItem);
}

• 然后对于每个新的股票条目，检查 map 中是否存在旧条目。如果存在，则创建一个新的库存条目，将旧条目和新条目结合起来。否则只需将新的股票条目添加到 map 中即可。

for (Stock newStockItem: newStock) {
    Integer stockCode = newStockItem.getStockCode();
    Stock oldStockItem = netStockMap.get(stockCode);
    if (oldStockItem != null) {
        Stock netStockItem = new Stock(stockCode, oldStockItem.getStockQuantity() + newStockItem.getStockQuantity(),oldStockItem.getStockValue() + newStockItem.getStockValue());
        netStockMap.put(stockCode, netStockItem);

    } else {
        netStockMap.put(stockCode, newStockItem);
    }
}

• 然后获取 map 的值作为最终的股票 list

List<Stock> netStock = new ArrayList<Stock>(netStockMap.values());