类型安全性：ArrayList []类型的表达式需要未检查的转换 [英] Type safety: The expression of type ArrayList[] needs unchecked conversion

问题描述

我正在一个项目中，我得到TypeSafety问题在初始化一个特定大小的方法。在我的run方法中，我在 new ArrayList [tableLists.size（）] 上有黄线并抱怨 -

I am working on a project in which I am getting TypeSafety issues on initializing one method with a particular size. In my run method, I have yellow line on the new ArrayList[tableLists.size()] and complaining about-

类型安全性：类型ArrayList []的表达式需要未检查的转换以符合ArrayList< Method> []

下面是代码。

private ArrayList<Method> methods[] = null;


    @Override
    public void run() {

        methods = new ArrayList[tableLists.size()];


    }

如何解决此问题 TypeSafety 在这里？

How can I fix this TypeSafety issue here?

更新： - b

    int j = 0;
    dbConnection = new Connection[tableLists.size()];
    callableStatement = new CallableStatement[tableLists.size()];
    methods = new ArrayList[tableLists.size()];

    //loop around the map values and make the connection list
    for (Map<String, String> map : tableLists.values()) {

        dbConnection[j] = getDBConnection(map.get("URL"), map.get("USER"), map.get("PASSWORD"), map.get("DRIVER"));
        callableStatement[j] = dbConnection[j].prepareCall(map.get("SQL"));

        methods[j] = getRequiredMethods(map.get("SUFFIX"));
        j++;
    }

推荐答案

t似乎以任何特定的方式分离，为什么不将它们全部存储在相同的 ArrayList 中，完全绕过问题？

Since the methods themselves don't seem to be separated in any particular way, why not just store them all in the same ArrayList, bypassing the problem entirely?

ArrayList<Method> methods;

/* ... */

methods.addAll(getRequiredMethods(map.get("SUFFIX")));

数组和泛型往往不会彼此发挥非常好。如果您真的需要分隔，您必须选择主要选项：

Arrays and generics tend not to play very nice with each other. If you really need the separation, you have to primary options:

1. 使用 ArrayList< ArrayList< Method>> 而不是数组。这将让你处理一切很好，而不使用平面数组。然后，您可以有效地初始化方法对象的大小就像一个常规的数组。

1. Use an ArrayList<ArrayList<Method>> instead of an array. This will let you handle everything nicely without mucking with plain arrays. You can then efficiently initialize the methods object with a size just like with a regular array.

methods = new ArrayList<ArrayList<Method>>(tableLists.size());

如果您真的需要使用数组，使用 @SuppressWarnings（unchecked）注释来抑制警告。这是丑陋和恼人，所以我会避免它，如果你可以。

If you really need to use an array, you'll probably have to suppress the warning using the @SuppressWarnings("unchecked") annotation. This is ugly and annoying, so I'd avoid it if you can.

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