Example of a Treemap using a Comparator?

Question

I'm in need of a small example of using a Treemap (with generics, of course) using a Comparator. For example:
TreeMap tm = new TreeMap<Foo,Short>(new ComparatorTest<Foo>());
for some class Foo, which I'm mapping to Short.
I've tried taking an old non-generic example and adding in the new pieces, but the java compiler isn't nice about indicating what I've done wrong.
Any examples out there?
Thanks

Answer 1

OK, I've fixed my declaration to be:
TreeMap<MppInfo,Short> tm = new TreeMap<MppInfo,Short>(new ComparatorTest<MppInfo>());
My code is:
class MppInfo {
public String badgeId;
public String mppRollupLevel;
public String month;
public String year;
class ComparatorTest<MppInfo> implements Comparator<MppInfo> {
public int compare(MppInfo a, MppInfo b) {
int val = a.badgeId.compareTo( b.badgeId );
if ( val != 0 ) {
return val;
val = a.mppRollupLevel.compareTo( b.mppRollupLevel );
if ( val != 0 ) {
return val;
val = a.month.compareTo( b.month );
if ( val != 0 ) {
return val;
val = a.year.compareTo( b.year );
if ( val != 0 ) {
return val;
return 0;
public boolean equals(Object o) {
MppInfo s = (MppInfo)o;
return compare(this, s) == 0;
...the java compiler does not like my code at all:
ReadMPP.java:436: cannot find symbol
symbol : variable badgeId
location: class java.lang.Object
int val = a.badgeId.compareTo( b.badgeId );
^
ReadMPP.java:436: cannot find symbol
symbol : variable badgeId
location: class java.lang.Object
int val = a.badgeId.compareTo( b.badgeId );
^
...deleting similar errors.
ReadMPP.java:457: compare(MppInfo,MppInfo) in com.ctc.PmPlanning.ReadMPP.ComparatorTest<MppInfo> cannot be applied to (com.ctc.PmPlanning.ReadMPP.ComparatorTest<MppInfo>,MppInfo)
return compare(this, s) == 0;
^
Note: ReadMPP.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
9 errors