Generics - Unchecked conversion warning

[O. Ziggy]

I cant figure out why i am getting this warning.

c:\scjptests\javac -Xlint ScjpSamples.java
ScjpSamples.java:1833: warning: [unchecked] unchecked conversion
found   : java.util.TreeSet
required: java.util.TreeSet<java.lang.Integer>
                setSubset = (TreeSet)setTimes.headSet(1600);
                            ^

For the following bit of code

                TreeSet<Integer> setTimes = new TreeSet<Integer>();
		setTimes.add(1205);
		setTimes.add(1305);
		setTimes.add(1405);
		setTimes.add(1505);
		setTimes.add(1605);
		setTimes.add(1705);
		setTimes.add(1805);
		setTimes.add(1905);
		setTimes.add(2005);

		TreeSet<Integer> setSubset = new TreeSet<Integer>();
		setSubset = (TreeSet)setTimes.headSet(1600);
		System.out.println("TreeSet - Last before 4pm - Java 5: " + setSubset.last());

both setTimes and setSubset are of type TreeSet<Integer>. I looked at the API and it is saying that TreeSet.headSet returns a NavigableSet<E> which has just confused me even more.

--

[Goerch Mosi]

Hello O.Ziggy,
because you forgot to define the type at the row where you use headSet(1600)

Try this one. ;-)

setSubset = (TreeSet<Integer>)setTimes.headSet(1600);

[O. Ziggy]

Thanks

[Henry Wong]

O. Ziggy wrote:
I looked at the API and it is saying that TreeSet.headSet returns a NavigableSet<E> which has just confused me even more.

NavigableSet is an interface that is implemented by the TreeSet class. A TreeSet IS-A NavigableSet. A NavigableSet is not necessarally a TreeSet. So... it may be a good idea to use NavigableSet instead, as the headSet() method may not always return an object that may be casted to TreeSet, in future implementations.

Henry