关于结果的java ArrayList

Question

    ArrayList<ArrayList<Integer>> result = new ArrayList<>();
    ArrayList<Integer> temp = new ArrayList<>();
    temp.add(1);
    temp.add(2);
    result.add(temp);
    temp.remove(temp.size() - 1);
    temp.add(1, 3);
    result.add(new ArrayList<>(temp));

结果是[[1,3],[1,3]],但我认为它应该是[[1,2],[1,3]],为什么？

Answer 1

关注评论

temp.add(1);  /aaded 1 
temp.add(2);  / added 2
result.add(temp);
temp.remove(temp.size() - 1); // removed index 1 that i.e removed 2
temp.add(1, 3);   // added 3 at the index 1 again.  now it is 1,3 
result.add(new ArrayList<>(temp));  // And you are added a new array list again with temp 

如果我理解正确,你会误解逻辑

 temp.add(1, 3);

这意味着您要告诉在列表3中的索引处添加值 .1temp