我如何访问列表的数组元素 [英] How I can access array elements of List

问题描述

我有一个问题:

我有一个用不同值填充的列表Java.例如，我有:

I have a List Java that I have populated with different values. For example, I have:

List<String[]> l = new ArrayList();
String[] lis = new String[3];
lis[0] = "A";
lis[1] = "B";
lis[2] = "C";
l.add(lis);

，我也有其他值.现在，我只想在此列表中的第一个字段中进行搜索.例如，我想要A的indexOf.我尝试编写以下代码:

and I have other values too. Now, I want to get the search in this list only the first field. For example, I want the A's indexOf. I have tried to write this code:

int index = l.indexOf("A");

但是我得到-1作为回报.我想知道在加载数组时如何访问列表的字段.

but I get -1 as return. I would like to know how I can access to a field of the list, when I load an array.

推荐答案

我想要A的indexOf.

I want the A's indexOf.

不，您无法获得它，因为它是数组中的一个元素.数组没有indexOf方法.列表中有该方法.

No, you can't get it, since it is an element inside array. Array doesn't have indexOf method. List have that method.

我想知道在加载数组时如何访问列表的字段.

I would like to know how I can access to a field of the list, when I load an array.

String firstElem= l.get(0)[0]; 

get(0)为您提供第一个插入的数组，[0]为您提供该数组中的第一个positiend元素.

get(0) gives you the first inserted array and [0] gives you the first positiend element in that array.

如果要在数组中查找 A 的位置，请使用 l.get(0)从列表中访问该数组，然后遍历该数组以获取 A 的位置.

If you are looking for position of A in array, access the array from list with l.get(0) and iterate over the array you got to get the position of A.

评论后更新:如果您不知道索引，则拥有

Update after comment: If you have no idea of indexes you have

for (int i = 0; i < l.size(); i++) {
        for (int j = 0; j < l.get(i).length; j++) {
            if( l.get(i)[j].equalsIgnoreCase("A")){
                return j;
            }
        }
    }

注意:请以以下示例代码为例，并添加对null，重复项等的检查...

Note: Consider that as a example code and add checks for null's ,duplicates etc ...

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