Explanation of ClassCastException in Java

Straight from the API Specifications for the ClassCastException:

Thrown to indicate that the code has
attempted to cast an object to a
subclass of which it is not an
instance.

So, for example, when one tries to cast an Integer to a String, String is not an subclass of Integer, so a ClassCastException will be thrown.

Object i = Integer.valueOf(42);
String s = (String)i;            // ClassCastException thrown here.

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