从ArrayList中删除两个受索引影响的元素

Question

I have 5 points from which I need to remove two for a total of three points. I need to remove two points of all possible combinations from 1-5. For example: 0,0 - 0,1 - 0,2 ... 5,1 5,2.. to the end.

for (int i = 0; i < newList.size()-1; i++){

            count = 0;
            ArrayList<Point> testList = new ArrayList<Point>(newList);

            while (count < K-1){
                testList.remove(i+1);
                count++;
            }

Here is what I had. The problem is, when I remove the first point, the index of the next point changes so I having a hard time keeping track of that.

I thought to use a double for loop like this:

for (int i = 0; i < newList.size(); i++){
        for (int j = 0; j < newList.size()-1; j++){

            count = 0;
            ArrayList<Point> testList = new ArrayList<Point>(newList);

            while (count < K-1){
                testList.remove(i);
                testList.remove(j);
                count++;
            }

But still, I get the following:

REMOVED: 0, 0
REMOVED: 0, 1
REMOVED: 0, 2
REMOVED: 0, 3
REMOVED: 1, 0
REMOVED: 1, 1
REMOVED: 1, 2
REMOVED: 1, 3
REMOVED: 2, 0
REMOVED: 2, 1
REMOVED: 2, 2
REMOVED: 2, 3
REMOVED: 3, 0
REMOVED: 3, 1
REMOVED: 3, 2
REMOVED: 3, 3
REMOVED: 4, 0
REMOVED: 4, 1
REMOVED: 4, 2
REMOVED: 4, 3

As you can see, there is a problem with printing out "5" in both columns because the index shifts when I make the first removal. Can anyone provide any suggestions?

Answer 1

To accomplish it use your previously created newList as reference and delete elements for testList that you have created.

while (count < K-1){
    testList.remove(newList.get(i+1));
    count++;
}

This way newList will be unchanged and will have all elements (ie Point ) and testList will have elements after removing that elements.

Answer 2

Make a filtered copy via standart library (eg guava collections ) or by manual copying:

List<Point> original = ...
List<Point> cleared = new ArrayList<Point>(original.size());
Set<Integer> dropIndex = new TreeSet<Integer>(Arrays.asList(2, 5, 128));

for (int i = 0, size = original.size(); i < size; i++)
    if (!dropIndex.contains(i))
        cleared.add(original.get(i));