从java中的列表中获取列表？

Question

First, I need to say that I tried found explanation in internet, but all are unclear for me.

I worte a program in java FX. One of classes has method generating two list:

listA = [0,2,3,4,1,2,5,12,3,2,1,3]
listB = [2,3,4,1,2,1,2,3,1,2,3,4]

I need to return that lists so I connect it in one:

ArrayList<List<Integer>> result = new ArrayList<List<Integer>>();
        result.add(listA);
        result.add(listB);
        return(result);

head of that method looks that:

static public List man() { #could be usefull to explain me how to fix my code.

So now in another class i call the method:

List newList= classTest.man();

And print it:

System.out.println(newList);

So I got:

[[0,2,3,4,1,2,5,12,3,2,1,3][2,3,4,1,2,1,2,3,1,2,3,4]]

And it's fine, I just want a write a loop to fill data for my chart:

for(int i; i < newList.get(0).length(); i++){
  String iterationNum= Integer.toString(newList.get(0).get(i);
  series.getData().add(new XYChart.Data<String, Number>(iterationNum; newList.get(0).get(i)));

But first:

1. .length() is red : error = "Cannot resolve symbol 'length'"

2. in newList.get(0).get(i) the second .get(i) is red. error = "Cannot resolve method 'get' in 'Object'"

Please, can someone help me solve my problem? I wrote almost whole of program, and stuck here.

Answer 1

length is red : error = "Cannot resolve symbol 'length'"

.length is used to get the length of an array. You are using, I assume, java.util.List . You need to use the method size , eg newList.get(0).size()

in newList.get(0).get(i) the second .get(i) is red. error = "Cannot resolve method 'get' in 'Object'"

static public List man() I'm not sure what this method does, but you are using a raw type. This means that the List you are getting back is basically equivalent to List<Object> .

So you are trying to call Object#get(i) , and get is not a valid method on an Object. You need to specify what type List man() will return. For instance, List<Integer> man() , or whatever type it needs to be. I can't tell from your code what you're actually doing.

Answer 2

1. ".length" is used to determine the Length of an array. For lists you use ".size()"

2. Try replacing it with ((List<Integer>) newList.get(0)).get(i);