ArrayList IndexOutOfBoundsException

Question

我正在尝试创建一个程序，它绘制一个具有指定边数的形状，但我一直收到错误，我不确定问题是什么。

public double tempx = 0;
    public double tempy = 0;
    public int Angle = 0;
    public double Length = 0;
    public int Nodes = 0;
    public int Height = 170;

    //public double xcoordinate = 0;
    //public double ycoordinate = 0;
    //Unused Variables

    /**
     * Creates new form Shape
     */
    public void drawShape(int Nodes,int Height){
        double Apothem=0;
        double Circumradius=0;
        double x = 180/Nodes;
        ArrayList<Double> xcoordinate = new ArrayList(Nodes);
        ArrayList<Double> ycoordinate = new ArrayList(Nodes);
        //Angle = (180*(Nodes-2))/2*Nodes;
        //Angle is half the interior angle of the shape(Currently Unused)
        Angle = 360/Nodes;


        if(Nodes%2==1){
            Length = (2*Height*Math.tan(Math.toRadians((x))))/(1+Math.cos(Math.toRadians((x))));
            Apothem = Length/(2*Math.tan(Math.toRadians((x))));
            Circumradius = Apothem/(Math.cos(Math.toRadians((180/Nodes))));
            System.out.println(Length);
            System.out.println(Apothem);
            System.out.println(Circumradius);
            //Calculating properties of an odd number of sides shape
        }
        if(Nodes%2==0){
            Length = Height*Math.tan(Math.toRadians((x)));
            Apothem = Length/(2*Math.tan(Math.toRadians((x))));
            //Calculating properties of an even number of sides shape
        }


        //double xcoordinate[] = new double[Nodes];
        //double ycoordinate[] = new double[Nodes];
        //Unused Variables

        if(Nodes%2 == 1){
                xcoordinate.add(1,Apothem);
                System.out.println(xcoordinate.get(1));
                ycoordinate.add(1,(double)0);
                for(int counter =2;counter<(Nodes+1);counter++){




                    xcoordinate.add((xcoordinate.get(counter-1)*Math.cos(Math.toRadians(Angle))-(ycoordinate.get(counter-1)*Math.sin(Math.toRadians(Angle)))));
                    ycoordinate.add((xcoordinate.get(counter-1)*Math.sin(Math.toRadians(Angle))+(ycoordinate.get(counter-1)*Math.cos(Math.toRadians(Angle)))));

                    //Uses Matrix Rotation to calculate all the coordinates of the point on the shape

        }
            }




    }

我目前正在尝试让奇数边形状工作，这是我在测试节点等于5时得到的输出：

136.55176280263456
Exception in thread "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Index: 1, Size: 0
93.97368876500715
116.15786740995709
    at java.util.ArrayList.rangeCheckForAdd(ArrayList.java:612)
    at java.util.ArrayList.add(ArrayList.java:426)
    at graphs.Shape.drawShape(Shape.java:58)
    at graphs.Shape.jButton1ActionPerformed(Shape.java:189)
    at graphs.Shape.access$100(Shape.java:10)
    at graphs.Shape$2.actionPerformed(Shape.java:140)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6505)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:723)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:682)
    at java.awt.EventQueue$3.run(EventQueue.java:680)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:696)
    at java.awt.EventQueue$4.run(EventQueue.java:694)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)

Answer 1

您正在使用add在索引1处插入对象，但是ArrayList中还没有任何内容，因此您不能将其插入到该位置。1比大小0大，所以你会得到一个IndexOutOfBoundsException。

我不确定哪一行是58行，但可能是这些行中的一行：

xcoordinate.add(1,Apothem);

ycoordinate.add(1,(double)0);

我不确定为什么需要在这一点上插入；通常add with just one argument会追加到列表的末尾，这应该可以很好地工作。

Answer 2

您正尝试在索引1处添加，但开始时数组列表为空--没有索引1。

只需使用常规的add即可。或索引0。

Answer 3

进行以下更改：

            xcoordinate.add(0,Apothem);
            System.out.println(xcoordinate.get(0));
            ycoordinate.add(0,(double)0);

第一个位置是0(不是1!!)。或者，您可以使用普通的add()方法：

            xcoordinate.add(Apothem);
            System.out.println(xcoordinate.get(0));
            ycoordinate.add(double)0);

这可能会导致将来出现问题：

            for(int counter =2;counter<(Nodes+1);counter++){

尝试设置计数器=1(因为ArrayList从0变为长度-1)