ClassCastException: [LResultImpl; incompatible with IResult


ClassCastException: [LResultImpl; incompatible with IResult

During unit test, the application throws exception that looks like: ClassCastException: [LResultImpl; incompatible with IResult.

At first, I am really curious, ResultImpl implements the interface IResult, why it can't cast ResultImpl object to IResult.

At last, we figured out that the [L means an array. it can not convert the array of ResultImpl to IResult.

This makes sense.

To verify:
public class ClassCast
{
    public static void main(String[] args)
    {
        // ResultImpl elment1 = new ResultImpl();
        IResult[] impl2 = new ResultImpl[] { new ResultImpl() };
        Object o = impl2;
        IResult result = (IResult) o;
    }
}

interface IResult
{
}

class ResultImpl implements IResult
{
}

Result:
Exception in thread "main" java.lang.ClassCastException: [LResultImpl; incompatible with IResult
    at ClassCast.main(ClassCast.java:10)
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