java - 如果数组列表中满足条件，如何比较元素并合并？

Question

我有交易列表，每个交易都有一些属性，例如现在的来源，从交易列表中，我想获取具有相同来源值(value)的所有交易，并将它们组合成一个交易，例如

tradeName      quote           source            quantity      price 
Google          GOOG           Goldman Sachs        15           610  
Microsoft       MSFT           Barclays             400          28
Google          GOOG           Goldman Sachs        45           610  
Google          GOOG           Goldman Sachs        40           610  
Microsoft       MSFT           Barclays             1000          28

现在根据源信息，我应该合并交易，所以我更新的交易列表将是

tradeName      quote           source            quantity        price 
Google          GOOG           Goldman Sachs        100           610  
Microsoft       MSFT           Barclays             1400           28

我不确定比较部分，如何解决？

<小时/>

尝试了以下方法，

for (Trade trade : tradeList)
{
   //Not sure how to compare this.trade.source with all sources 
   //of all trades present in the trade.
   //Logic should be if source matches then quantity should be added 
   //but am not sure how comparison would work.  
}

Class Trade
{

private tradeName;
private quote;
private source;
private quantity;
private price;

//Getters and Setters for each of above mentioned attributes. 

}

Answer 1

我想我会创建一个 HashMap<String, Trade> ，使用tradeName+quote+source作为键，然后将列表中的每个交易添加到 map 中的相应项目。

示例:

Map<String, Trade> map = new HashMap<String, Trade>();
for (Trade trade : tradeList) {
    String key = trade.tradeName + "#" + trade.quote + "#" + trade.source; // signature, what you merge by 
    if (map.containsKey(key)) {
        map.put(key, trade); // the first trade with such a signature 
    } else {
        // not the first, so merge it with the existing one
        map.get(key).add(trade); // you'll have to implement the Trade.add() method
    }
}
List<Trade> merged = new LinkedList<Trade>(map.values());