将3个arraylist合并为一个

Question

我想在java中合并3个arraylist.有谁知道哪种方法最好？

Answer 1

使用ArrayList.addAll().像这样的东西应该工作(假设列表包含String对象;你应该相应地改变).

List<String> combined = new ArrayList<String>();
combined.addAll(firstArrayList);
combined.addAll(secondArrayList);
combined.addAll(thirdArrayList);

更新

我可以通过您的评论看到您实际上可能正在尝试创建2D列表.如果是这样,以下代码应该起作用:

List<List<String>> combined2d = new ArrayList<List<String>>();
combined2d.add(firstArrayList);
combined2d.add(secondArrayList);
combined2d.add(thirdArrayList);

Answer 2

使用java.util.Arrays.asList来简化合并怎么样？

List<String> one = Arrays.asList("one","two","three");
List<String> two = Arrays.asList("four","five","six");
List<String> three = Arrays.asList("seven","eight","nine");

List<List<String>> merged = Arrays.asList(one, two, three);