匿名添加对象时从ArrayList获取特定对象？ [英] Get specific objects from ArrayList when objects were added anonymously?

问题描述

我已经创建了一个简短的问题示例。我正在匿名创建对象列表并将它们添加到 ArrayList 。一旦项目在 ArrayList 中，我稍后会回来并向列表中的每个对象添加更多信息。如果你不知道它的索引，有没有办法从列表中提取特定的对象？

I have created a short example of my problem. I'm creating a list of objects anonymously and adding them to an ArrayList. Once items are in the ArrayList I later come back and add more information to each object within the list. Is there a way to extract a specific object from the list if you do not know its index?

我只知道对象的'名字'，但你不能做 list.get（ObjectName）或其他任何内容。建议的方法是什么？每次我想要检索一个特定对象时，我宁愿不必遍历整个列表。

I know only the Object's 'name' but you cannot do a list.get(ObjectName) or anything. What is the recommended way to handle this? I'd rather not have to iterate through the entire list every time I want to retrieve one specific object.

public class TestCode{

    public static void main (String args []) {
        Cave cave = new Cave();

        // Loop adds several Parties to the cave's party list
        cave.parties.add(new Party("FirstParty")); // all anonymously added
        cave.parties.add(new Party("SecondParty"));
        cave.parties.add(new Party("ThirdParty"));

        // How do I go about setting the 'index' value of SecondParty for example?
    }
}

class Cave {
    ArrayList<Party> parties = new ArrayList<Party>();
}

class Party extends CaveElement{
    int index;

    public Party(String n){
        name = n;
    }

   // getter and setter methods 

    public String toString () {
        return name;
    }
}


class CaveElement {
    String name = "";
    int index = 0;

    public String toString () {
        return name + "" + index;
    }
}

推荐答案

鉴于使用 List ，没有办法在没有迭代的情况下查找一个值......

Given the use of List, there's no way to "lookup" a value without iterating through it...

For例子......

For example...

Cave cave = new Cave();

// Loop adds several Parties to the cave's party list
cave.parties.add(new Party("FirstParty")); // all anonymously added
cave.parties.add(new Party("SecondParty"));
cave.parties.add(new Party("ThirdParty"));

for (Party p : cave.parties) {
    if (p.name.equals("SecondParty") {
        p.index = ...;
        break;
    }
}

现在，这需要时间。如果您要查找的元素位于列表的末尾，您必须在找到匹配项之前迭​​代到列表的末尾。

Now, this will take time. If the element you are looking for is at the end of the list, you will have to iterate to the end of the list before you find a match.

可能更好使用某种地图 ......

It might be better to use a Map of some kind...

所以，如果我们更新洞穴看起来像......

So, if we update Cave to look like...

class Cave {
    Map<String, Party> parties = new HashMap<String, Party>(25);
}

我们可以做类似......

We could do something like...

Cave cave = new Cave();

// Loop adds several Parties to the cave's party list
cave.parties.put("FirstParty", new Party("FirstParty")); // all anonymously added
cave.parties.put("SecondParty", new Party("SecondParty"));
cave.parties.put("ThirdParty", new Party("ThirdParty"));

if (cave.parties.containsKey("SecondParty")) {
    cave.parties.get("SecondParty").index = ...
}

相反......

最终，这将是全部取决于你想要达到的目标...

Ultimately, this will all depend on what it is you want to achieve...

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