将对象的 ArrayList 列表转换为对象 [][] [英] Convert List of ArrayList of Objects into Object [][]

问题描述

有谁知道如何转换二维列表:

Do anyone have an idea how to convert 2 dimension List:

private List<ArrayList<Object>> data = new ArrayList<ArrayList<Object>>();

进入数组:Object [][] data; ?我注意到 data.asList(new Object[i][j]);只返回 1 个维度，如 T[].当然 j 维总是常数.

into array: Object [][] data; ? I noticed that data.asList(new Object[i][j]); is returning only 1 dimension like T[]. Of course j dimension is always constant.

推荐答案

您可以使用 for 循环并调用 toArray() 用于每个内部列表.

You could use a for loop and call toArray() for each inner list.

Object[][] arr = new Object[data.size()][];
int i = 0;
for(ArrayList<Object> list : data){
    arr[i++] = list.toArray();
}

使用 java-8，您可以将每个内部列表映射到一个数组，然后构造结果数组:

With java-8, you could map each inner list to an array and then construct the resulting array:

Object[][] arr = data.stream().map(List::toArray).toArray(Object[][]::new);

这篇关于将对象的 ArrayList 列表转换为对象 [][]的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！