What is SuppressWarnings (“unchecked”) in Java?

Question

Sometime when looking through code, I see many methods specify an annotation:

@SuppressWarnings(\"unchecked\")

What does this mean?

Answer 1

One trick is to create an interface that extends a generic base interface...

public interface LoadFutures extends Map> {}

Then you can check it with instanceof before the cast...

Object obj = context.getAttribute(FUTURES);
if (!(obj instanceof LoadFutures)) {
    String format = "Servlet context attribute \"%s\" is not of type "
            + "LoadFutures. Its type is %s.";
    String msg = String.format(format, FUTURES, obj.getClass());
    throw new RuntimeException(msg);
}
return (LoadFutures) obj;