Java Applet AWT-EventQueue-1 ArrayIndexOutOfBoundsException

Question

I created a Vector called lines that stores the coordinate points of the end points of drawn line. It accomplishes the task that I want by drawing lines from the stored coordinates but produces the following exception:

Exception in thread "AWT-EventQueue-1" java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 10
    at java.util.Vector.get(Vector.java:748)
    at DrawPad.paint(DrawPad.java:149)
    at java.awt.Container.update(Container.java:1995)
    at sun.awt.RepaintArea.updateComponent(RepaintArea.java:255)
    at sun.awt.RepaintArea.paint(RepaintArea.java:232)
    at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:358)
    at java.awt.Component.dispatchEventImpl(Component.java:4967)
    at java.awt.Container.dispatchEventImpl(Container.java:2294)
    at java.awt.Component.dispatchEvent(Component.java:4713)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.awt.EventQueue$4.run(EventQueue.java:731)
    at java.awt.EventQueue$4.run(EventQueue.java:729)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

score 0 · Answer 1 · answered Nov 25 '15 at 20:33

0

Your problem is most likely here:

for(int i = 0; i < lines.capacity(); i += 4)
            g.drawLine(lines.get(i), lines.get(i + 1), lines.get(i + 2), lines.get(i + 3));

You are incrementing i by 4 each iteration of the for loop. Which means the first loop you are accessing the 0, 1, 2, and 3 elements of the lines Vector. The next loop you are accessing 4, 5, 6, 7. Next you are accessing 8, 9, 10, 11. The lines Vector may not have that many elements in it.

answered Nov 25 '15 at 20:33

Josh Chappelle

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I have to look at 4 points at a time ... Each time I press and then release my mouse, it adds 4 points. – Mutating Algorithm Nov 25 '15 at 20:43
1

Create a Line object that has 4 integers in it. Each time you add a line, add a new Line(1, 2, 3, 4) to your lines Vector. Then your loop will just iterate over each line object like so: for(int i = 0; i < lines.capacity(); i++) g.drawLine(lines.a, lines.b, lines.c, lines.d); – Josh Chappelle Nov 25 '15 at 20:47
1

I'll edit my answer so I can post the formatted code – Josh Chappelle Nov 25 '15 at 20:49
Scratch what I said about the line object. I added a new answer. – Josh Chappelle Nov 25 '15 at 21:02

score 0 · Accepted Answer · answered Nov 25 '15 at 21:02

0

You need to check to see if the element exists before calling lines.get(i). Also, use lines.size() instead of lines.capacity().

for(int i = 0; i < lines.size(); i += 4)
{
    if((i+3) < lines.size())
    {
        g.drawLine(lines.get(i), lines.get(i + 1), lines.get(i + 2), lines.get(i + 3));
    }
}

answered Nov 25 '15 at 21:02

Josh Chappelle

1,558
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Awesome. Glad I could help. – Josh Chappelle Nov 25 '15 at 21:16
I deleted the code since this was an assignment and I didn't want other students finding it. Just for your information. – Mutating Algorithm Nov 25 '15 at 21:17

Java Applet AWT-EventQueue-1 ArrayIndexOutOfBoundsException

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