选择arraylist中的元素并交换到下一个元素和前一个元素

Question

我的疑问是如何在ArrayList中选择一个元素，这样我就可以在下一个元素中交换，我希望将元素向下移动并交换到前一个元素，然后移动项目。

public class ShapesFX{

        private ArrayList <Shape> shapes;

        public ShapesFX() {
            this.shapes= new ArrayList <> ();
    }

  / **
     * Swap positions with the immediate previous element. The method can not
     * Be successful if the reference element is the last.
     *
     * @ Param element element reference to the exchange
     * @ Return true if the exchange was successful. false, d.c.
     * @ Throws Exception if the element does not exist
     * /

    @ Override
    public boolean moveUP (Shape element) throws Exception {
        if (element != null) {
            throw new Exception ("Element does not exist");
        } else if (element != Null) {
            for (FormaGeometrica sh : this.shapes) {
                if (sh == element) {
                    Collections.swap ((List<Shape>) element, 0, 0);
                }
            }
            return true;
        }
        return false;
    }

  / **
     * Swap positions with the next immediate element. The method can not
     * Be successful if the reference element is the first.
     *
     * @ Param element element reference to the exchange
     * @ Return true if the exchange was successful. false, d.c.
     * @ Throws Exception if the element does not exist
     * /

    @ Override 
    public boolean moverDown (Shape element) throws Exception {
        if (element != null) {
            throw new Exception ("Element does not exist");
        } else if (element != Null) {
            for (Shape sh : this.shapes) {
                if (sh == element) {
                    Collections.swap ((List<Shape>) element, 0, 0);
                }
            }
            return true;
        }
        return false;
    }

如果这个方法是正确的，输出的一个例子是

--- List of Figures ---
F1
F2
F3
F4

--- Move F2 UP ---
F2
F1
F3
F4

F2 change position with F1

--- Move F3 DOWN ---
F2
F1
F4
F3

F3 change position with F4