删除彼此相邻的重复项

Question

I have a list: private static List<Point> pointList = new ArrayList<>(); .

Point = object representing a point in 3D graph.

I can compare Points with method:

@Override
public boolean equals(Object o) {
    if (this == o)
        return true;
    if (o == null || getClass() != o.getClass())
        return false;
    Point point = (Point) o;
    return Arrays.equals(position, point.position);
}

Lets say my list looks like that: { a1, a2, b1, a3, c1, c2, a4 }

All objects are different objects (a1 =/= a2..), but have same values ( a1, a2... representing exact same point on graph)

What I want is to remove duplicated Points that are next to each other on list, so list would look like that { a, b, a, c, a }

I tried:

public List<Point> getUniq() {
    List<Point> l = new ArrayList<>();
    for (int i = 0; i < pointList.size()-1; i++) {
        if (pointList.get(i).equals(pointList.get(i + 1))) {
            l.add(pointList.get(i));
        }
    }
    return l;
}

But I'm missing elements.

Answer 1

You basically need to keep reference to the last added object. If the object that you are currently trying to add is the same, then you should skip it.

Here is how it would look like using your code:

public List<Point> getUniq() {
    List<Point> result = new ArrayList<>();
    Point lastAdded = null;
    for (int i = 0; i < pointList.size(); i++) {
        if (!points.get(i).equals(lastAdded)) { // previously added point was different
            lastAdded = points.get(i); // update previously added
            result.add(lastAdded); // add to result
        }
    }
    return result;
}

Answer 2

Your code does not seem to do what you want according to your description.

What I want is to remove duplicated Points that are next to each other on list, so list would look like that { a, b, a, c, a }

The following piece of code should do the work:

public List<Point> getUniq() {
    List<Point> l = new ArrayList<>();
    l.add(pointList.get(0)); //the first element will always be added
    for (int i = 1; i < pointList.size(); i++) {
        if (!l.get(l.size()-1).equals(pointList.get(i))) {
            l.add(pointList.get(i));
        }
    }
    return l;
}