TreeSet error

[a]

I have the following problem, where the Song is a class created by me. The
first add is ok. The second caused this error.

Exception in thread "main"
java.lang.ClassCastException: library.Song
at java.util.TreeMap.compare(Unknown Source)
at java.util.TreeMap.put(Unknown Source)
at java.util.TreeSet.add(Unknown Source)
at library.Album.main(Album.java:82)

public static void main(String[] args){
Album a = new Album("JimmySongs");
Song s0 = new Song("LoveSong0",1);
Song s1 = new Song("LoveSong1",2); <-----Caused ERROR

TreeSet<Song> s = new TreeSet<Song>();
TreeSet<String> t = new TreeSet<String>();
t.add("ONE");
t.add("TWO");<--------------------OK
s.add(s0);<--------------------OK
s.add(s1);<--------------------ERROR
Thanx a lot

[Nemo]

In message <E7r4f.199507$oW2.131760@pd7tw1no>, a <[e-mail]> writes

I have the following problem, where the Song is a class created by me. The
first add is ok. The second caused this error.

Exception in thread "main"
java.lang.ClassCastException: library.Song
at java.util.TreeMap.compare(Unknown Source)
at java.util.TreeMap.put(Unknown Source)
at java.util.TreeSet.add(Unknown Source)
at library.Album.main(Album.java:82)
Does your Song class implement Comparable?

See Java documentation for TreeMap for details.

public static void main(String[] args){
Album a = new Album("JimmySongs");
Song s0 = new Song("LoveSong0",1);
Song s1 = new Song("LoveSong1",2); <-----Caused ERROR

TreeSet<Song> s = new TreeSet<Song>();
TreeSet<String> t = new TreeSet<String>();
t.add("ONE");
t.add("TWO");<--------------------OK
s.add(s0);<--------------------OK
s.add(s1);<--------------------ERROR
Thanx a lot

--
Nemo (ne**@stian.demon.co.uk)