[英]Java initialize 2d arraylist
I want to do 2D dynamic ArrayList example: 我想做2D动态ArrayList示例:
[1][2][3]
[4][5][6]
[7][8][9]
and i used this code: 我用这个代码:
ArrayList<ArrayList<Integer>> group = new ArrayList<ArrayList<Integer>>();
group.add(new ArrayList<Integer>(1, 2, 3));
how should i initialize this arraylist? 我应该如何初始化这个arraylist?
If it is not necessary for the inner lists to be specifically ArrayList
s, one way of doing such initialization in Java 7 would be as follows: 如果内部列表不必是特定的
ArrayList
,那么在Java 7中进行这种初始化的一种方法如下:
ArrayList<List<Integer>> group = new ArrayList<List<Integer>>();
group.add(Arrays.asList(1, 2, 3));
group.add(Arrays.asList(4, 5, 6));
group.add(Arrays.asList(7, 8, 9));
for (List<Integer> list : group) {
for (Integer i : list) {
System.out.print(i+" ");
}
System.out.println();
}
Use 使用
group.add(new ArrayList<Integer>(Arrays.asList(1, 2, 3)));
The ArrayList
has a Collection
parameter in the constructor. ArrayList
在构造函数中有一个Collection
参数。
If you define the group
as 如果将
group
定义为
List<List<Integer>> group = new ArrayList<>();
group.add(Arrays.asList(1, 2, 3));
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