CODEWITHSUNDEEP
javacastingclasscastexception
TeaCupApp
TeaCupApp

Reputation: 11452

Why I cannot type cast with (Point2d.Double)? - Java

I have below code snippet - Which doesn't work.

private void startAddingTrackPointValue()
    {
        Set<Point2D.Double> keySet = this.trackPointList.keySet();
        Point2D.Double[] keys = (Point2D.Double[]) keySet.toArray();
        for(int i = 0; i < keys.length; i++)
        {
            System.out.println(keys[i]);
        }
    }

Which generates exception is, This...

Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.awt.geom.Point2D$Double;
    at SegmentFactory.startAddingTrackPointValue(SegmentFactory.java:170)
    at SegmentFactory.<init>(SegmentFactory.java:44)
    at TestClass.main(TestClass.java:8)

But this works fine, If I do it like this,

private void startAddingTrackPointValue()
    {
        Set<Point2D.Double> keySet = this.trackPointList.keySet();
        Object[] keys = (Object[]) keySet.toArray();
        for(int i = 0; i < keys.length; i++)
        {
            System.out.println(keys[i]);
        }
    }

Question is, why can't I typecast with Point2D.Double[]?

Upvotes: 2

Views: 1926

Answers (2)

jtahlborn
jtahlborn

Reputation: 53694

because "Object[]" is not an instance of "Point2D.Double[]".

neither of these will work:

Point2D.Double[] = (Point2D.Double[])new Object[0]; // this is essentially what your code is doing
Point2D.Double = (Point2D.Double)new Object();

do this instead:

Point2D.Double[] keys = (Point2D.Double[]) keySet.toArray(new Point2D.Double[keySet.size()]);

Upvotes: 3

Joey
Joey

Reputation: 354614

Pass a typed array to toArray():

Point2D.Double[] keys = keySet.toArray(new Point2D.Double[keySet.size()]);

Upvotes: 1

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