Java:如何将一个 ArrayList 拆分为多个小 ArrayList? [英] Java: how can I split an ArrayList in multiple small ArrayLists?

问题描述

如何将一个 ArrayList (size=1000) 拆分为多个相同大小 (=10) 的 ArrayList?

How can I split an ArrayList (size=1000) in multiple ArrayLists of the same size (=10) ?

ArrayList<Integer> results;

推荐答案

您可以使用 subList(int fromIndex, int toIndex) 以查看原始列表的一部分.

You can use subList(int fromIndex, int toIndex) to get a view of a portion of the original list.

来自 API:

返回此列表中指定的 fromIndex(包含)和 toIndex(不包含)之间的部分的视图.(如果fromIndex 和toIndex 相等，则返回列表为空.)返回列表由该列表支持，因此返回列表中的非结构性变化反映在这个列表，反之亦然.返回的列表支持此列表支持的所有可选列表操作.

Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive. (If fromIndex and toIndex are equal, the returned list is empty.) The returned list is backed by this list, so non-structural changes in the returned list are reflected in this list, and vice-versa. The returned list supports all of the optional list operations supported by this list.

示例:

List<Integer> numbers = new ArrayList<Integer>(
    Arrays.asList(5,3,1,2,9,5,0,7)
);

List<Integer> head = numbers.subList(0, 4);
List<Integer> tail = numbers.subList(4, 8);
System.out.println(head); // prints "[5, 3, 1, 2]"
System.out.println(tail); // prints "[9, 5, 0, 7]"

Collections.sort(head);
System.out.println(numbers); // prints "[1, 2, 3, 5, 9, 5, 0, 7]"

tail.add(-1);
System.out.println(numbers); // prints "[1, 2, 3, 5, 9, 5, 0, 7, -1]"

如果您需要这些切碎的列表不是视图，那么只需从 subList 创建一个新的 List.以下是将其中一些内容组合在一起的示例:

If you need these chopped lists to be NOT a view, then simply create a new List from the subList. Here's an example of putting a few of these things together:

// chops a list into non-view sublists of length L
static <T> List<List<T>> chopped(List<T> list, final int L) {
    List<List<T>> parts = new ArrayList<List<T>>();
    final int N = list.size();
    for (int i = 0; i < N; i += L) {
        parts.add(new ArrayList<T>(
            list.subList(i, Math.min(N, i + L)))
        );
    }
    return parts;
}


List<Integer> numbers = Collections.unmodifiableList(
    Arrays.asList(5,3,1,2,9,5,0,7)
);
List<List<Integer>> parts = chopped(numbers, 3);
System.out.println(parts); // prints "[[5, 3, 1], [2, 9, 5], [0, 7]]"
parts.get(0).add(-1);
System.out.println(parts); // prints "[[5, 3, 1, -1], [2, 9, 5], [0, 7]]"
System.out.println(numbers); // prints "[5, 3, 1, 2, 9, 5, 0, 7]" (unmodified!)

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